Maybe two strikes late or something. But the ref was in there and watching it intently, got himself in a good position to see (better than this camera angle), and seemed to care what was going on.
In terms of late stoppages, I've seen a lot worse. He didn't go limp or out...not like Shane Carwin jackhammering Mir's lifeless head. And as was mentioned, he seemed to be covering up with his right hand. I've seen guys in that position suddenly explode and attempt to escape while taking similar shots.