The fact remains that the sentence "He looks as if he had seen a ghost" is statistically aberrent to UK speakers of English because active percepton will assign it "meaning" equivalent to the "has" version.
Hello again, Fresco. I allowed that that was the case. I wrote,
"Which is the most commonly used of the three above? Probably 'has seen', but that doesn't exclude the others."
And I'd say that that would be the case for NaE as well.
I guess my point wrt that is, that is what Tanguatlay should have been told at the outset, that this particular construction is uncommon, not that tenses must match.
Where this feeling of aberration comes from could be explained by reference to culture, perhaps using the model of Chomsky's transformational grammar in which "had seen" (surface structure) is a culture specific transformation of "has had the experience of seeing some time ago" (deep structure). Note that the "difference" between the "has" and "had" versions can only be substantiated by assuming the "some time ago" sub-context...but this will only occur by juxtaposing the "has" and "had" versions...without such juxtaposition the versions remain semantically equivalent with the second grammatically aberrent (to some).
These considerations are my reasons for using the word "simplistic".
I agree with you, there's no doubt that many of these choices are culturally/dialect "centrically" induced, Fresco. One excellent example is the greater tendency for speakers of BrE to use the present perfect.
Might I suggest that what seems to be grammatically aberrant only reflects our tendency to seize on the most likely context.
Just a random thought; do you think that this same "some time ago" sub-context applies in the case of reported speech?
A: I have recently been to Spain.
B: What did he say, C?
C: He said that he had recently been to Spain.