Note: The term spawn displacement is not accurate, as actually your spawn point is still where it usually is but you spawn with horizontal velocity. I'll still use this term in this post tho.

I do agree that spawn displacement performed before a run should be banned, but I don't see a reason why spawn displacement performed in-game (respawn displacement maybe) is not allowed.

It is simply that, you inherit some portion of the horizontal velocity when you respawn, if your horizontal velocity before the respawn was above somewhere around 25.

The speed requirement can be achieved with SSG, and could be useful in some scenarios (e.g. thermal cp2-3).

Given that some otherworldly black magic trickery like pinch is allowed, I don't see why spawn displacement which is performed in-game should be banned.