*Patience Fuji*...
It seems like he stopped his regen. You are saying that its just because its more AP. When its clearly something else.
He is also not a Gorosei and a godamn High tier.
I hope this makes sense to you.
I think it is just the case that strong haki delays regen.
We saw with Saturn how he couldn’t regen instantly from Kuma’s punch or even Luffy’s punches.
Meanwhile Gunko instantly regenerates from Usopp’s attack.
In any case until we get next chapter, it’s very debatable if Gaban actually bypassed regeneration.