Don't you worry, It was not hard.
All It would have taken was to remember that even Kinemon didn't react for a whole fucking arc in front od the treasure of Wano. And Zoro used It literally in front of him:
That already made clear how agenda driven was for some to think the Scrabbards not reacting at a sword never used they saw from afar in literally one scene was just agenda.
I mean, I whole arc >>> a scene and Shusui >>> another BB, not to mention not even used, and still.