They're a contributing factor in some cases, but the combination of framing of the forearm across the chin, the back of the head taking the contact. Sometimes just the force or landing on the head wrong is enough to sleep someone. Other's can take some crazy slams and recover such as Fedor against Randleman. You get slams like when Vinc Pinchel got slammed there was 0 headbutt involved. Tonight's one I believe had a headbutt similar to Rampages and like rampages, I think it helped contribute but it wasn't the decider, I do think under video review these finishes could be DQs or NCs depending if the headbutts are intentional or not however that would damage marketing ability.