I think I remember something about participants lean mass gain slowing down/plateauing after a given amount of time and there's so many other explanations for that. Then the idea that lean mass shoots up again (or they start working) after not using them for a given amount of time seems like it could be as simple as glycogen, water and your body reaching the point of homeostasis for the given hormonal situation.

If I can be overly simplistic, if 500mg test makes you gain 10lbs of water and glycogen and adds 10% to your strength just through the CNS. It would logically follow that each month after that the effects (lean mass/strength) would slow down and eventually plateau (due to just the 500mg test) unless stimulated enough to continue growing. So they might technically slow down but through diet and weight training you could still achieve more than you could on cruise or naturally

Kinda like how puberty works in boys, we experience a certain period of increased lean mass gain but it doesn't continue linearly and eventually plateaus unless stimulated

I hope someone can dig up the study. I just felt like rambling and throwing my thoughts out there and see if anyone has anything to add