That's really the equalizer for fighters like them. You never know where their heads will go during the fight. Brock was able to keep his head on straight during the Carwin fight and ate many bad motherfuckers, but kinda ran scared from Cain (and others, been a while so I can't remember, probably better examples than Cain). If the result of the reaction to getting tagged is up in the air, you're beatable. I seem to remember Kayla kinda going full early 00s Vitor when Pacheco broke her will, too. Just kinda gave up. That isn't a quality of an unbeatable fighter.