BJ has one punch KO power as displayed in his past fights, he doesn't chose to go for the one shot. If BJ sees an opening for the KO, he's going to take it.
Yes I am using Lyoto as an example considering he's twice the striker GSP is, and he is much more heavier and stronger. Lyoto Machida who has KO'd Rich Franklin, and rocked numerious of natural middleweights/light heavyweights like Tito Ortiz, Nakamura, Sokodjou etc. wasn't able to rock or hurt and overweight BJ Penn who looked like was pregnet. You can make the point BJ arguably won that fight.