60gr was the ticket for a few decades, but both the Russians and US are beefing up their rounds to keep up with advances in light armor and target protection. Consider that the 47rnd weighs about 125gr, and 6.5 Grendel & 6.8 Rem are very close, as is the 6.5 Swede. The 6.x rounds have very efficient shapes similar to the 5.45 or 77gr SMK in 5.56.
A long, thin 6.5x40 steel core, hollow tip with a wee bit of taper to aid cycling action is about optimum for today's battles. Maybe he saw it coming and feels that it is better to carry fewer rounds of bigger bullets.

Afghanland is mostly wide open or long shots between mountains.  Fighting in urban areas in Chechnya has shown the 7n6 round to lack penetration.

They are starting to use more "enhanced penetration" rounds. I forget the designation right off the top of my head.

They are having the same problem the US is having in urban areas and their mouse gun round.  It won't go through obsticals.

Remember, he came from a different era when 7.62 X 54R was king for his country.  He would have different ideas on what makes a good round. To some degree he was right, but it did not match "modern needs".

As for having enough 7.62 X 39 on hand - it sounds like a good arguement, but look at this example, in 1944, the Germans had 8,000,000,000 rounds of 8mm Mauser on hand, they did all they could to switch over to a new and better round while under constant bombing.  If it is better and there is a need, it will be made.

In the end, their round is alot more lethal that the ones we carry.

That is highly debatable, especially against the newer 75 and 77 grain fragmenting loads.

Its all more lethal than the 7.62x39 except for the newer M67 type ball and the best 5.56 ammo beats it by a wide margin(wehn we are talking what is hague convention legal).