Smooth as butter with Firefox on Android. As for why scrolljacking is "allowed", web devs will always find new ways to do annoying things and work around browser constraints.
I confirm that. Then I opened the page in Chrome on Android and it scrolls nicely there too. So maybe they broke only desktop browsers.
I swear. Put me off so bad I didn't even bother reading the rest of the article. It's even more infuriating that this is by a company this big