I don't think that's true at all. It's all just speculation here, but I think Trouba tries to line people up for big hits, obviously, but he's pretty damn slow and deliberate, so guys are able to get out of his lane. He then realizes that he's f***ed and the guy he's checking is about to go completely around him unobstructed so he just desperately and recklessly tries to get some contact with the player. He's not reaching out with his arm because that's also obvious and he'll get his shoulder separated, so he stupidly throws the elbow out.
Again, all just speculation. But I honestly don't think he's ever thinking, 'I'm going to elbow this guy in the head,' he's just big, slow and very, very reckless.
Also, I should note that I don't think this should absolve him of punishment. You need to be in control of your stick at all times, you should also have to be in control of your limbs at all times.