A captain being stronger than their subordinate doesn't mean they are better than them in every single way. That has always been true.
Katakuri had better CoO than Big Mom and nobody questioned it. Yet, when the manga makes it clear King is harder to damage than Kaido, by having greater durability and endurance, and all of a sudden it's questioned and told that can't happen.
Kaido increasing his overall strength doesn't increase his durability. It's the same since he fought Oden. Similar to how Luffy's rubber body keeps the same durability. Even in awakening, Luffy's rubber body is vulnerable to cutting attacks.
Why are you using rooftop Zoro's feat and power level instead of post ACoC Zoro's power who has much greater power.
Oda hardly allow characters to lose limbs or be cut in half so that excuse doesn't work. Remember, Mr.1 used a cutting attack that somehow cut the pillar behind Zoro into pieces but couldn't do the same to Zoro.
King's wings are more durable than Kaido's body/scales. That is fact and the manga proves it. The same attack from Zoro that easily cut through Kaido's body/scales couldn't cut through King's wings.
Zoro's statement about the wings blocking the attack tells us the wings it's just tanking the attack. The wings stopped the attack from getting through.
It's irrelevant if they are wings instead of arms. It's a fictional manga so Oda can make wings as hard and durable as he wants.
Everything I have posted is facts. I used manga scene to support my post. You claiming it's not does change it.