Linux supports a variety of compositing managers (programs that receive pixels from the application and are responsible for actually making the video hardware draw them), and these each have various settings that control how they interact with blanking. I have mine set to sync to vblank and so Chrome animations seem to sync to vblank too. Changing the settings on the fly, though, is implementation dependent, and whatever implements the feature for this website probably doesn't want to bother.
It does work fine on ChromeOS, so it's a "generic Linux" thing, not some specific problem with the Linux kernel itself.
It does work fine on ChromeOS, so it's a "generic Linux" thing, not some specific problem with the Linux kernel itself.