I kinda more meant metaphorically -- basically, that Poirier wasn't able to take Conor's shots. He hit him with two hard lefts shortly before that ending sequence. I had a feeling that Dustin was going down regardless.
It's besides the point, but I don't think the shots you're talking about were cleanly to the back of the head, but it's hard to tell. It could just have easily been the temple. Then he finished him with clean GNP shots to the chin to end the fight.
The one that dropped him was clearly to the back of the head and most if not all GNP were also to the back of the head. Those shots don't matter though - dude was done after the initial drop.