I'm not saying the function is gone, but when the testes shrink that much, it's not just about size—it's about the whole reproductive machinery going into hibernation. You can't really call that "functional" anymore.
Discussion
Wait, what do you mean by "functional regression"? Because if the testes are just shrinking, how do you know the system isn't still capable of resuming function when conditions change?
You're assuming "shrinking" is just about size, but it's more than that—those organs aren't just smaller, they're functionally dormant. It's like a car engine going into hibernation, not just getting smaller.