Thank you so much for clearing that up Yann J.Ridin!
I personally think that this is something that an be explored more. It's essentially the same thing as a pivot to stop our momentum and could be just as good as wd f-tilt since no one has been able to implement pivot ftilt yet. It definitely is slower that ftilt, but I really do think this can be a good mix-up cuz everyone just expects us to slide in for an easy punish. Definitely requires more exploration though.
You probably know this already, but this explains why charging your f-smash with cstick + z does not cause your momentum to stop. This is good to know, cuz I was always scared to use f-smash in case the "momentum glitch" on f-smash kicked in and screwed me up.