I doubt the figure of 72,000 it was much more, already the Confederation of the Rhine - along with the Poles (which Sokolov conveniently ignores) would exceed this number plus French troops.
One has to take into account that Russia is a vast country, again, where would they concentrate their units? The border makes a lot of sense and due to the hyperaggressive politics of Napoléon a war was unavoidable - so good common sense would dictate that concentration.
This would give a lot of options for strategy - or operational moves in case Russia was attacked - which finally worked out.
Surprisingly Russia did not attack N - in case one would believe the 72,000 figures and peacefully waited for the invasion