Why in the world would Einstein suggest... 2

I don't know, but this discussion is not making much progress.

Frames of reference are mathematical tools necessary to calculate motion, distances, speed, etc. of other mathematical objects. Such frames are concepts existing only in the mind. They are not physical objects. Even when a frame of reference is "anchored" on a physical object, it is NOT the same thing as the object.

Do you agree with the difference I have shown between LR and SR in the 120 hour train example? If not, why not?

Another point is that you don;t actually know what you disagree with, since SR and "LR" actually say the same thing, for all practical purposes, yet you will agree with one and disagree with the other...

Do you agree with the difference I have shown between LR and SR in the 120 hour train example? If not, why not?

The short answer to your question is: over a period of 120 hours, neither a train nor the earth surface can reasonably be considered inertial. Therefore there is no reciprocity in SR between frames anchored on these objects

Anyway, I tried.

I think it's much simpler than that: you are bent on disagreeing with SR, and that's why you keep inventing your own strawman version of SR, easier to tear down than the real one. That's also why you are not interested in understanding what I say.

Also discovered the philosophic side of Pointcarre thanks to this debate, and will dig that further.

Poincaré's work in the development of special relativity is well recognised...Poincaré developed a similar physical interpretation of local time and noticed the connection to signal velocity, but contrary to Einstein he continued to use the ether-concept in his papers and argued that clocks in the ether show the "true" time, and moving clocks show the local time

...neither a train nor the earth surface can reasonably be considered inertial.

Pointcarré contributed to SR by helping Lorentz develop his equations, and pointing at time dilatation as being a profound intuition rather than just a computation device. Apparently he was pissed off that Einstein did not acknowledge his debt to him.

In 1572, Tycho Brahe noticed in the heavens a new star. An immense conflagration had happened in some far distant heavenly body; but it had happened long before; at least two hundred years were necessary for the light from that star to reach our earth. This conflagration therefore happened before the discovery of America. Well, when I say that; when, considering this gigantic phenomenon, which perhaps had no witness, since the satellites of that star were perhaps uninhabited, I say this phenomenon is anterior to the formation of the visual image of the isle of Española in the consciousness of Christopher Columbus, what do I mean?

A little reflection is sufficient to understand that all these affirmations have by themselves no meaning. They can have one only as the outcome of a convention. [...]

Behold then the rule we follow, and the only one we can follow: when a phenomenon appears to us as the cause of another, we regard it as anterior. It is therefore by cause that we define time; but most often, when two facts appear to us bound by a constant relation, how do we recognize which is the cause and which the effect? We assume that the anterior fact, the antecedent, is the cause of the other, of the consequent. It is then by time that we define cause.

We say now post hoc, ergo propter hoc; now propter hoc, ergo post hoc; shall we escape from this vicious circle?

I shall ask him first how he knows it, that is, how he has measured the velocity of light. He has begun by supposing that light has a constant velocity, and in particular that its velocity is the same in all directions. That is a postulate without which no measurement of this velocity could be attempted. This postulate could never be verified directly by experiment...

no matter whether a chronometer is used, or whether account must be taken of a velocity of transmission, as that of light, because such a velocity could not be measured without measuring a time.

The simultaneity of two events, or the order of their succession, the equality of two durations, are to be so defined that the enunciation of the natural laws may be as simple as possible.

To conclude: We have not a direct intuition of simultaneity... We replace it by the aid of certain rules..
These rules are not imposed upon us and we might amuse ourselves in inventing others; but they could not be cast aside without greatly complicating the enunciation of the laws of physics, mechanics and astronomy.

This line of reasoning reminds me of the Minkowski diagram, according to which Tycho Brahe's supernova explosion is NOT in any meaningful sense anterior to Colombus' voyage across the pound.

From all these results, if they were to be confirmed, would issue a wholly new mechanics which would be characterized above all by this fact, that there could be no velocity greater than that of light, any more than a temperature below that of absolute zero....(1904)

Perhaps, too, we shall have to construct an entirely new mechanics that we only succeed in catching a glimpse of, where, inertia increasing with the velocity, the velocity of light would become an impassable limit.(1904)

There is no absolute space, and we only conceive of relative motion ; and yet in most cases mechanical facts are enunciated as if there is an absolute space to which they can be referred. 2. There is no absolute time. When we say that two periods are equal, the statement has no meaning, and can only acquire a meaning by a convention....is not our Euclidean geometry in itself only a kind of convention of language?" (1901)

"Whether the ether exists or not matters little – let us leave that to the metaphysicians; ...some day, no doubt, the ether will be thrown aside as useless." (1889)

"It appears that this impossibility of demonstrating the absolute motion of the earth is a general law of nature.(1904)

However, Poincaré himself never abandoned the ether hypothesis..And although he admitted the relative and conventional character of space and time, he believed that the classical convention is more "convenient" and continued to distinguish between "true" time in the ether and "apparent" time in moving systems. Addressing the question if a new convention of space and time is needed he wrote in 1912:[A 20] "Shall we be obliged to modify our conclusions? Certainly not...

was talking of all inertial frames of reference being equivalent to calculate time dilatation, and about non-inertial frames not offering the same equivalence. This has nothing to do with the effect of acceleration on time dilatation. These are two different topics having no bearing with one another.

It's often said that special relativity is based on two postulates: that all inertial frames are of equal validity, and that light travels at the same speed in all inertial frames. But in real world scenarios, objects almost never travel at constant velocity, and so we might never find an inertial frame in which such an object is at rest. To allow us to make predictions about how accelerating objects behave, we need to introduce a third postulate.

This is often called the "clock postulate"...clock postulate says that the rate of an accelerated clock doesn't depend on its acceleration...The clock rate won't be affected by circular motion at constant speed....

The clock postulate also implies that the amount of shortening of a moving rod is independent of its acceleration. And also, that the relativistic mass of a moving object also doesn't depend on its acceleration....it's a statement about the physical world...Although the clock postulate is just that, a postulate, it has been verified experimentally up to extraordinarily high accelerations,