Tbf, "Enma" is not a well thought out PU and quite honestly, made everything a mess.
If Enma is sucking zoro's coc, then zoro shouldnt fluctuate his KoH state. In theory, he should always be in KoH mode during a fight because Enma is always sucking him off.
It doesn't make sense that it turns on/off.
Sanji's exoskeleton SEEMS to be tied to Sanji's state of mind. It usually happens when he's pissed. So at least there's consistency in that and you can get behind this explanation. State of mind changes, so exoskeleton turns on/off. nice.
Enma doesn't change. Enma is Enma. KoH shouldnt go on/off randomly.