performance.now resolution in Chrome is between 1 and 2 ms, I believe, with jitter. If they have a working POC for Chrome why not demonstrate the full exploit and force the Chromium team to rethink their mitigations? Lots of people talking possibilities but zero working exploits in the open. That's not a good ground for rational debate.
Timers aren't necessarily even a requirement to exploit Spectre: https://hackertimes.com/item?id=22831067. It's pretty hard to protect against this in general unless you generate retpolines.
