Yeah, nerfed, but 30%? I would still believe you if you had said that he has lost 30% of his strength.
Luffy has been ko'd directly from Ragnarok, before upgrading his haki, and was ko'd due to stamina loss due to poor control of his new haki, but apparently Luffy is at 100% fresh according to some.
Kaido hasn't been KO'd, and his
passive zoan ability that he is using
while fighting, (that Momo, with the same fruit, most likely is going to have to go
all out to replicate and save the captial), is waning
slightly, after reaching the place he already pre-planned to drop Onigashima. This passive ability faltering slightly means Kaido is under half health apparently, before even going into awakening.