Browsers made a fundamental change a while back to not share caches between origins because caching it became a side-channel to detecting if someone had visited it before.

So now if two different websites embed the same remote font then visitors will have to download it separately for both sites.

https://developer.chrome.com/blog/http-cache-partitioning

Surely one of the most popular browsers in the world could ship with some commonly requested fonts and all you'd learn is that they were using chrome which the user-agent said anyways.