What part of the argument exactly are you disagreeing with?
That warhead numbers went down at all, or that the reductions were attributable to arms control?
If the latter, see my above post - fiscal pressures from the collapse were plainly not so severe as to preclude retaining a lot of expensive delivery systems, or the development of new ones. By maintaining a higher number of warheads per delivery vehicle, Russia could have kept a substantially larger arsenal quite easily.
If the former, well, if we assume for argument's sake that warhead numbers didn't go down in the first place, what relevance does the collapse of the USSR have at all?