You are pulling some real mental gymnastics here.
Every time Luffy has needed to go in and out of G4, he’s always been able to function normally or basically after that. WCI, Wano proved that.
Every time Luffy uses up all his G4 haki, he is a cripple for 10 minutes. Dressrosa, WCI, Wano proved that.
That is literally it. Simple and shonen. This is shonen not rocket science.