Why wait the hell with that??? Tell me now
this is the perfect chapter for you dispute my points.
1. We learn that there are swordsmen who can cut nothing. (Examples Shown in manga:Roger,Shanks,Xebec)
2. These same swordsmen can cut through steel and with the same instrument. (Example shown in manga: Shanks- cuts through steel rail gun, does not cut through Kidd. Shanks does this with the same instrument and the same attack Divine departure)
3. Pinnacle of swordsmanship is to protect what one wishes to protect (example:shanks protecting his fleet) and cut (example: railgun) what one wishes to cut (example: does not cut Kidd)
Roger intent was to test oden not kill him so he sends him flying because of his intent akin to xebec sending things flying with his swordsmanship, but at the same time if he wants to he can cut a mountain based on his intent.
Edit: reminder we learn in wano that this is ryou which is armament haki