I haven't timed it, so I don't know.

My video doesn't show the fastest way to kill this phase by jumping from the bottom, it seems like. I might record a video of me messing around with that, but keep in mind that I'm a complete noob when it comes to speedrunning this game (as opposed to casually playing it).

Here's the video I (kind of) promised: These are several attempts at this strat. Some of them were successful, like the first one. Apologies for forgetting to adjust the sound volume.

Yeah looks faster if you get it right