It depends on what YOU call receivers. Is that the upper receiver that is maintained for normal replacement? Or do you mean the lower trigger mech housing that isn't made for normal maintenance purposes? I don't know the answer officially of course but it all makes sense to me. There were xxx,xxx rifles made for an army of 120,000 at the time PLUS the Navy and RAF since 1986, 30 years don't forget. There have been a few wars and general fair wear and tear since '86 taking the numbers down considerably. So to maintain the was reserve stock it seems sensible to keep stockpiles up. And if that means building more rifles then so be it.
I don't know what you have heard about the L85A2 rifle. While most of the slagging-off of the A1 was justified - within the bounds of sensibility, there are/have been little to complain about with the A2 rifle.