I personally don't want it to be allowed, makes movement more of a hardware thingie than skill.
https://www.razer.com/technology/snap-tap-mode
read through it and if you dont understand lmk ill explain better
Flash kick socd is pretty much the same thing as snap tap, two opposite directions (up/down) makes sure that up is always prioritized even when both are pressed down. That is quite literally what snap tap does, just in a more niche scenario.
However, given the nature of fighting games, hitbox is 100000 times more broken then snaptap
Wooting also gives an unfair advantage but because almost every pro uses Wooting nobody really cares. Probably will be a similar situation with this one.
Also remember that in regular lobbies nobody is playing a fair game at a hardware level to begin with. If my CPU and GPU are better than yours, I'll get more FPS. If my monitor is better than yours, I'll see you before you see me. If my mouse has a better sensor, I'll have better control over my aim. Not sure where the line should be drawn since hardware is becoming stronger and stronger.