Nah, I don't think it was on purpose tbh. By that time in the fight, those guys were tired, and Alvarez was just probably just going by habit (maybe related to your "not consciously" comment, puukallistaja). He was kneeing Porier, and being tired, it was like second nature for him to keep hitting his opponent. Again, just my opinion based on what I saw.

Replay of the knee and post fight interview, if anyone is interested. Even more respect for Porier after watching this again. Guy seems like a good dude. Sounds like both want the rematch, so hopefully it'll be sooner than later.