Why pawn h3?

www.youtube.com/watch?v=MqOseqNUhHk&list=PLQsLDm9Rq9bHwqL_f-6OzC4OowhoVRfxd

In this video by ChessNetwork, he moves the pawn to h3 pretty early in the game and makes an off-hand comment about not allowing the dark squared bishops to exchange. Could someone explain to me what the thought behind the h3 move is?

I think he misspoke. It seems like he's trying to avoid the light-square bishop exchange, not the dark-square bishop exchange. By playing h3, he limits the scope of black's light-square bishop, not allowing it to go to g4 with tempo. He doesn't want to lose his knight for that bishop (because the bishop is doing nothing and will struggle to get into play), which is why he plays h3 before Nf3.

Thank you :)