What pushing Mantha's buttons accomplishes (if it takes) is it gives you a bull in a china shop that busts his ass every night. Imagine if Franzen could internalize the power stuff he did against the Avalanche in the playoffs and just play every game that way. You'd have an unholy terror on your first line. Same with Mantha. Get him to play his ass off 100% of the time and you have a rocket fast skater with a deadly shot who backchecks and becomes one of those potential core players everyone drones on about missing.
And also, it's a hell of a lot to correct bad habits when you're learning your craft than when you've already learned your craft. It is a lot easier to, in the immediate aftermath, say "Tony, the hell are you doing? You need to close off that point man. Watch what Hank or Darren do" than if you wait until Mantha is the BMOC and you try saying it. It's a little bit like training a dog. You can't see something they did wrong and then criticize them several weeks, months, or years later. If you want to change habits, you need to get on them ASAP.
This complaint is more about AA than Mantha, but there are plays were average fan looks at AA and sees "that dude quit on a play" or "he's just not skating hard". Not mistakes, exactly, but very evident lapses in effort. They see that he can skate like lightning to capitalize on a breakaway but all of a sudden can't catch Benoit Pouliot when he has to play some defense.