This is a carry-over from the add-on. https://github.com/firefox-devtools/Gecko-Profiler-Addon/issues/158

Florian wrote:

It seems we are never able to sample more than every 2ms on Windows, so I think we should increase the default sampling interval (currently 1ms) to 2ms.

Opening an issue here for tracking, but this may need a patch in mozilla-central and a change in the Gecko Profiler add-on.

Equivalent on the Gecko side: https://bugzilla.mozilla.org/show_bug.cgi?id=1574816