atsch Staying physically fit while you are in between fights and maybe even doing light sparring is not the same as training for an actual fight.
Dont think it makes much difference, Mosley was blowing badly at the end of the Cotto fight and his reflexes looked poor in that fight as Cotto was able to hit him with clean punches and slide underneath him, his poor reflexes and condition were not that surprising, particularly as the Cotto fight was in 07. If you watch the Margarito fight Mosley did not have to work very hard as he was allowed to hold a lot, that in turn cut off Margarito's supply line, he could not make Mosley fight harder because he was holding so much, although i guess its concievable he did over-train, not that it would of mattered either way.
No ****. But if you're staying active and keeping in shape, it's a lot easier to deal with the rigors of training.
Whether he was keeping in shape or not it's not impossible to be overtrained as your post alluded to. Along with rigorous training there is the process of cutting weight which is a reality in preparing for a real fight that is not the reality when you are just staying in shape; furthermore training camps are a certain amount of time for a reason. I am not trying to take away from PBFs victory but it's a possibility like Cotto stated.