I think this was sped up because it does goes way too fast at the slope

I have just checked the video and did tests on the in-game timer and the fall speed The timer started and ended at the same as mine, the switch tween 60/59 and 30/29 happen together The fall speed is also the same (you can use "," and "." key to advance frame b) frame)

No noticeable pitch change for the audio in that section, the highest point was further than normal jump from the slope, which a sped-up recording will not make it become possible (with the flower as reference)

At the moment, I believe the record is legit