Just for perspective, 20-25 years ago people often said the same things about 10mm as you're saying about the 9mm. The 10mm was "way underpowered" compared to the 44 Magnum (which, back then, was often considered the "bare minimum" in these conversations). Just because someone lives in AK, doesn't mean they have any real level of knowledge about handgun ballistics and their actual use in bear defense.
The popularity of the 10mm is more about guys wanting the most "powerful" auto available, and the fact that there are a lot more 10mm options available now. It's become "okay" in group-think to carry the 10mm in the last 10 or 15 years because of shifts to auto platforms over revolvers, in general, not because the 10mm has been shown to be "superior" or even the equal of, e.g., the 44 Magnum, etc.
I've never met a guy who carries a 10mm who also has any knowledge about its actual terminal performance compared to a 9mm. I have met guys that carry a 10mm for bear defense that think a guy using a 9mm for bear defense is going to die, for sure. Their thought that there's that much difference between the two is never coming from any level of knowledge about the subject. Exactly the opposite, actually.
FWIW, on Kodiak this week, between 4 guys, two carried pistols (when they were bow hunting). One carried a 9mm, one carried a 10mm, no one said a single word about that, whatsoever. Maybe not as big a deal as you're thinking it is.