Shiki required 3 days of fighting sengoku and Garp, remember
Luffy himself didn’t beat Kaido in a clean 1v1
there is no rule that Oda doesn’t diminish feats of “legends”… we were told that Whitebeard’s claim to fame was that he could fight Roger and then when we saw it on panel, it’s revealed to have been a joke fight… Whitebeard has never actually fought serious Roger…