50 or 60 years ago that was the conventional wisdom of the day. That's no longer the case. Today the 10mm Glock 20 loaded with Buffalo Bore 220gr is the go-to bear defense pistol. If you carry a revolver for bear defense in Alaska you're probably at least 80 years old.
Yes, the 10mm is becoming popular.
But it is not a magic wand.
It is a 200gr bullet at about 1200fps.
I have found the S@W 2.0 in 10mm to fit my hand better allowing for faster follow up shots.
The Glock 20 grip just too big for many.
Any handgun caliber that gives you approximately the same ballistics. Works just fine.
If one owns a good revolver or other handgun of appropriate caliber no need to trade it in on a 10mm.