You were bullshitting about how Yamao, someone below Yonko level could injure Green Bull -> downplaying Admiral's durability.
As if the current Yonko with highest bounty wouldn't get injured by the same attack, while he already lost his arm to fucking fish in weakest sea.
He didn't fucking defend, Shanks wasn't using any abilities at all to increase power or durability, he willingly gave up that arm, albeit it has some plot holes due to the fact that he could have just knocked it out with haoshoku but it wasn't planned too well at the start. But, on the other side, Green Bull was transformed and probably using Haki against the scabbards, and Yamato (probably) slammed him like she did to Kaidou. Like obviously that attack Yamato used would hurt most if not all characters, but it's overall effect would differ due to the differing durability in characters, and I'm certain that Shanks could probably block/take it well since he was able to block Akainu's magma punch and very likely has advanced forms of haki considering the other Yonkos ( with feats ) all have it.