That's the one thing that i've hard kyokushin people have trouble with when transitioning to MMA. I watch an interview with Bas where he said that's the trouble he had when he stepped into MMA from Kyokushin.
Bas went from TKD to Kuyokushin to Muay Thai (Thai Boxing) THEN to MMA...
Just being a stickler.
But yes, the rule sets often dictate where the weaknesses in a fighting system will to be.