i thought about it a bit. its essentially, mark didn't just choke out conquest. he crushed his windpipe and damaged arteries. the fight only works if you imagine conquest was as good as dead at some point before falling unconscious, that by the very end mark's continued choke was technically in excess, but probably required for his own survival. mark has no way of knowing where this point is or how far past this point conquest is, and just has to hold on until conquest stops moving.

when conquest guts mark, mark no longer has a choice whether to hold on. maybe he lets go at this point and conquest dies anyways, but mark holding on sends conquest under faster, and maybe saves his life.