Reading this https://wicki.io/posts/2020-11-goodbye-google-fonts/ , my thought seems to go in an unusual direction: Browsers are partitioning their caches?
They're probably doing it to prevent timing attacks. Similar to Spectre, but not a CPU-level vulnerability.
But it immediately struck me as a probable performance regression. I reckon network timings shouldn't be exposed to webpages, but doing so would once again break most JS. JS was a mistake!