TLKY, I take your word for that, but, the fact remains that nearly everyone pronounces all the vowels almost the same and there are too many current variations for it to all be authentic.
My example from England was, I thought, an excellent illustration. I’m not aware that they have a mesorah to say a sh’va as a kamatz; it’s obviously a dialectical issue that came via their exposure to their host country.
As well the example of yumtev and yuntiff: again, liShitasam, it should be yoimtoiv. (As pronounced, “yumtev” is actually closer to a cholam than choylam.) So where did yumtev come in? Again, it must be a local corruption.
So these other variations, like choylam, also are likely attributable to the same thing.
Is this not clear? Luhavdil, look at the different pronunciations in American English? LA, Chicago, NY, FL, TX, et al. have some pretty noticeable differences. But, for Lishon HaKodesh, we’re talking about mesorah, not culture.
So why are these variations still being perpetuated?