I think it’s stupid to make absolutes on something like muscle gain. It is highly individual and I think it varies a great deal for the same person. I hate it when people try to be all sciency and say “no you cannot gain any more than ½lb of dry muscle per week… because I know everyone’s genetics”. Not to mention it’s dumb as shit to try and actually base your whole diet around ‘optimising’ the amount of muscle you’ll gain in a week.
You simply cannot accurately predict the exact quantity of something as non linear as muscle. Putting hard and fast rules like that only serve to limit potential progress, imo.
Also, I will admit I don’t know the details here (and please correct me if I am wrong), but I doubt most of the pro’s gave a shit exactly how much muscle they could build in a week or even a year when they started training seriously. It seems like they put most of their attention on just getting their poundages up and eating enough to fuel that kind of training and get the physical growth from it.
I think agonising over exactly how much muscle can be gained ‘optimally’ is mostly for the people who can’t seem to eat enough or train hard enough to make a whole lot of progress in the first place.