Facepalm.
Yep you can't even answer that because there is no valid answer other than this:
If he does one fight in that division, then henceforth it is a weight division he has fought in. If he plans to fight more in that division (which he stated he does multiple times), that makes it a division he fights in.
It wasn't a one time thing. Unless you think McGreggor is lying to the public and you know his true plans to shy away from any future fights in welterweight division?
He might have a championship belt in featherweight, but he also fights in lightweight and welterweight. Not sure how you can argue otherwise but feel free.
Umm, he's stating a fact. He's fought in a division where his size and weight compared to his opponents allowed his strikes to be more effective. I think he was analyzing why he punched himself out but still could not stop Diaz with punches. He also stated that he was in panic mode at one point.
Excuses can also be facts. It's like a basketball team playing an away game in another arena, and attributing their loss to the fact that the stadium was different than what they are used to in their home court... It might be fact that it played a roll in their loss, but it's also an excuse and poor sportsmanship. It's like saying they didn't lose because the other team was better, but rather they lost because of the home court advantage. (even though nate diaz has fought more lightweight matches than welterweight so its not really his home court either.).