I think you are spot on about Benavidez. He didn't square up and really expose himself until Plant was in trouble and David was walking through his punches.
I do think the 1968 pound limit might be a problem for Benavidez, and I think he overtrained for this fight.. He was very light and looked gaunt before the fight. 166.5 is very light for him. And he couldn't get his punches off until later in the fight. I was surprised that he wasn't jabbing until late in the fight.
I also think if Kenny Baylwss' interruptions saved Caleb from being stopped a few times, and he was admonishing David when he should have been admonishing Plant.
Benavidez vs Canelo would be a great fight, but I think DB might be a tall order for Canelo. This was actually a bad night for DB, and in the end, Plant was struggling to survive. Canelo is better than Plant, but he has his pace that he likes to go. DB is much more active, and he doesn't have to worry about someone with foot speed like Plant. Should be a great fight. And I don't think there is any way Canelo can avoid it, unless he fights Romero