Not sure about others, but as far as I know high resolution timers were removed to (partly) mitigate side channel attacks.
https://webkit.org/blog/8048/what-spectre-and-meltdown-mean-...
https://webkit.org/blog/8048/what-spectre-and-meltdown-mean-...
My longstanding belief & understanding was that Safari was deliberately crippling cross-tab interactions. This felt like a marked place where Safari had did the right thing, and simply decided what was good for the web was bad for Apple. But I don't know where I'd go to find evidence or citations.