Zoro did fight Kaido in a 1v1.
The scene shows Zoro deflecting Kaido's attacks before he cut and scar him.
Yes, Kaido did tank his attacked just like he did everybody else attack. Zoro attack still caused Kaido more damage than anybody else. Scarring him is the way the manga showed Zoro caused him significant injury. Zoro attack made Kaido start shaking and breathing heavy.
It's a mode. He's so far has three different attacks with it.