When Zoro learned BOAT, he can choose to cut a Rock or not Harm a Leaf at will, it's like the target is at the mercy of his Will
Against Kaido however, both Oden and Zoro weren't able to cut Kaido at command, they simply managed the feat by exerting so much Power
They basically forced their way in, their Attacks surpassed Kaido's Defense, and likes of Mihawk, Roger ... etc can do that too
But that's not what BOAT is about, Peak Swordsmanship is when the Target is cut simply at your Will, if you simply power up your Attack then that's just simply creating a Strong enough attack to harm your target and potentially kill them
BOAT "Ignores" the Material and simply cuts it without any resistance. But those who can Kill Kaido aren't ignoring his Defense, they are Beating it
So EOS Zoro must prove his BOAT is Greatest Ever, he can cut anything by just swinging his Sword, no need to go all out