First off let’s establish the pinnacle of swordsmanship as told by and demonstrated by Koshiro.
Zoro here learns some very important details to swordsmanship.
1- Zoro’s own understanding is confirmed some swordsmen can cut through anything, even steel!!!
Really only including this to restate Zoro wanting to CUT through anything same childhood goal Koshiro.
2- Koshiro tries to teach him some swordsmen can NOT cut anything, these same swordsmen also have the ability to cut through steel. And with the same instrument.
The desire of the swordsman is key and at this point I feel pretty confident that we have two displays of this.
Roger vs Oden… Haki slash sent to him but no cuts anywhere on Oden’s body afterwards Roger is one of those swordsmen who can not cut anything.
Next example being his pupil Shanks using the same attack which mind you left no cuts on Kid.
3- The Pinnacle of Swordsmanship is the power to protect what one wishes to protect and cut what one wishes to cut.
Shanks demonstrated this fully in Chapter 1079. First he wanted to protect everyone, secondly we need to remember that a swordsman that can NOT cut, can cut steel. Shanks did all this in that moment he cuts through the rail gun and then does not cleave Kid in two the pinnacle of swordsmanship, so many are saying Shanks is using a sword but not cutting anything therefore he is not a swordsman when Oda has already established this as still being swordsmanship.