as far as I know it wasn't really "patched" and V2 being anchored to the ground in 1-4 is probably unintended in the latest patches.
I imagine it was unintentionally patched out since its not in patch notes, but if it was intentionally patched out the work around for current patch would be to try and land under where V2 lands and get your hitbox to nudge V2's mid-air movement towards center at the start of the fight but it both sounds and looks hellish to go for so for now atleast I'd just reccomend down patching if you really want to lower your time.
Anything pre P-2 would work. Patch 8/16/22 would be the most recent.
If you have not seen ULTRAKILL is finally having a speedrunner competition for real money!!! It starts in about four hours from the time I am making this news post, in fact its probably already started when you are reading this so click the challenges widget on the right and read up on the rules and