I would not argue the point that it is adequate for game under 200lbs. You are essentially talking 7.62X39 class performance which is about on par at 200 yds with 30-30 to give you some perspective. 30-30 gives you 30 more grains and 100fps more speed at the muzzle.where do you get that information that shows it has been "recognized for years" and recognized by whom?
I know a lot of AR owners who would argue that 120 gr. doing 2400 is more than adequate for game under 200 lbs. and even larger if you listen to some of them.
I have read Russian hunting materials which did not recommend 762X39 and as we know that cartridge was not designed as a hunting round. However more recent material suggests that for Russian boar 762X39 is doing its part if the shooter does his part.