@oralloy,
By now, I'm not sure explanation is available. As I said, you'd be better off reading some books on semantics and the evolution of and changes in language - it's no where near to as clear cut as you think. I used to think things were quite black and white (with some grey). But there have been plenty of things I've encountered over time that I went 'I doubt that exists'....until I started reading into it.
In relation to language, I found that studying another language also helps. It helps clarify some of the very loose ways we use language, and definitions. And you helps us understand how words really just represent concepts, and some of those concepts are hard to pin down (obviously many are easier to define).
But all of that could be nebulous. A book has enough space to dedicate example after example, with lengthy explanations.
I could look at either of your definitions and find little to argue about...other than because of the repercussions of the definition. Does magazine size really come into it ? Someone draws a line in the sand and says it's 25...so a manufacturer makes the same rifle with a 24 mag attachment...a technicality.
As I mentioned though, the real battle, or motivation behind the semantic argument, is whether or not they should be on the street. That's really why it's futile (except, maybe, as a short term measure). If they can't get it blocked as an assault rifle (which I'm guessing is currently the easiest battle ground), they'll look at creating a new category that will still result in it being banned.
It doesn't achieve anything in this forum to argue it. Perhaps to refine your arguments...but if it's not making headway, then is it really achieving anything? I don't think so, though you are welcome to disagree.