I thought of this a bit over the summer and was then reminded of it when I saw Professor X training with CT and going back to barbells shoulder pressing.
Lets say someone can barbell shoulder press 225x5 at some point and then for whatever reason has 6 months off from training. They come back and begin with barbell shoulder press again and due to muscle memory the size and strength come back relatively quickly. But I think most of us would agree that until he beats that 225x5 (assuming this is his main shoulder movement) he'll mostly be getting back lost size.
So in the case of someone just switching exercises and not taking time off (like Professor X), he may switch out BB shoulder press and go for machines. Over the next year or so he gets much stronger on the machines and his shoulders grow.
Then he switches back to BB shoulder press and due to so much time away from it he's currently down to 185x5 (not likely for beginners/intermediates but certainly advanced guys can come back weaker on an exercise even if getting stronger on other related ones). Even though he has even more muscle than he did a year ago so it's not like he'd be regaining lost muscle, would he not make any muscular gains from that exercise until he beats his previous best?
I'm not entirely sure, it's a hypothetical question really that I doubt many people could know for sure, but I'm interested to hear peoples thoughts. My thought would be that he wouldn't make muscular gains off that exercise alone until he gets past his previous best (assuming same tempo and other factors being the same) because he's mostly gaining neural coordination and whatnot until that point.
So it could be weeks/months before new growth from that particular exercise. Personally I have kept most of my exercises the same during my cut for similar reasoning (that my muscles would be more likely to be maintained than switching to new ones and just getting better coordinated with the movement, etc.)