"Kaido went easy and heavily held back vs Luffy pré G5, G5 can at worst mid diff G4 and at best no diff G4 Luffy."

What Kaido used vs Luffy pré G5:

Kaido used V1 Hybrid form, Dragon form, Acoc, Acoa, Futuresight, V2 Hybrid form, many named acoc attacks even spammed Thunder Below Bagua on Luffy and went drunk which amped Kaido Haki. He only didn't use two moves that is Death destroyer and flame Bagua

Kaido vs G5 Luffy:

Kaido wasn't drunk anymore, nowhere implied he ever used Futuresight vs G5, didn't use Lightning Drunk Ragnarok, a weaker version of Ragnarok did ragdoll overpower Giant G5. Kaido used the stronger version of Drunk Ragnarok on pré G5 Luffy and Luffy tanked that and kept going. He did use Death destroyer and Flame Bagua vs G5.

Kaido was exhausted and heavy breathing vs Luffy pré G5 and even stated that Luffy was going toe to toe with him, that's Kaido literally saying that Luffy pré G5 is in same tier as Kaido, that is Yonkou level.

This same Kaido that went high to extreme diff vs Luffy pré G5, went extreme diff vs G5 Luffy. In no world G5, Kaido or anyone can beat pré G5 Luffy below High diff.