Very odd, I can reproduce this also. Looks like something to do with the scroll velocity.
After several random tests, it appears to be triggered by first scrolling a bit with a trackpad (I used my built-in trackpad on an M1 Air), then switching to a magic mouse and scrolling, and it will trigger this behavior. I was able to reproduce this on several other websites. You have to close + reopen tab to reset the issue, and if you do that and then just scroll with magic mouse, it works fine.
It also scrolls fine if you scroll on the mouse without lifting your finger, but if you swipe up or down and release your finger, which typically does an inertia scroll, it buries you at the very bottom of a page, and any further inertia-swipes up or down keeps you down at the bottom for me.
(Also wanted to say that your setup in the video is freakily similar to mine with macbook + external Dell monitor, mechanical keyboard w/ white + gray keys, and a Fulla Schiit preamp...!!)