Baer looked against Braddock like he didn't want to win at all. It's not how he looked in other fights. He clowned against Carnera, but he still attacked and destroyed him. He clowned against Foord, Levinsky and Galento but he wasn't disinterested. He didn't clown against Schmeling and that was his best filmed fight. Baer from Levinsky/Schmeling/Carnera fights was extremely damgerous.
Even a seriously minded Baer would struggle with Berbick at his best. Not claiming that Trevor was any all time great.. No where near it, he could be an absolute nut case at times, but he'd make someone work for it or even pull of a surprise win time to time. Did well going fifteen with Larry and well for beating Thomas. Baer's not KOing him I'm pretty sure, Berbick had a not bad punch to, he'd get Max's respect imo.
Even if that's the truth (and you can't be sure with a hitter like Baer), Maxie won quite a few decisions. He was always well conditioned at least until getting the title.