i'm guessing that this is because safari doesn't allow the layout code (or anything else) to run while it's scrolling, which with normal websites (which don't use fixed positioning for everything) results in less janky experiences, and was famously critically important to get reasonable scrolling on the original iphone. it doesn't matter how fast clay's algorithms are if they're not allowed to run

(otoh when i try to load the web page it doesn't work at all, not even jankily, if we're talking about https://www.nicbarker.com/clay)