FreeSync (G-Sync compatible) testing with Firefox: Regressions in 430/435 drivers?

So I recently updated to the latest Vulkan beta of the Nvidia drivers to find Firefox (Waterfox) started to draw 2fps lower than the native refresh rate when in full screen. This is extremely annoying when viewing fullscreen 60fps videos on YouTube.

The TestUFO Refresh Rate counter is where this issue is most apparent. On a proper driver like the 418 series, the refresh rate is properly 59.995hz in full screen, but on the 43x.xx drivers, the refresh rate is 57.555hz.

This is the TestUFO refresh rate counter:

I need testing for this if you have G-Sync Compatible and you use Firefox. This has been nagging me since I installed the new drivers, and by downgrading the driver, the regression went away. Unfortunately, the older driver has issues with memory management in Vulkan which the latest driver fixes, only to have this ridiculous problem in Firefox.

Maybe someone else can post their findings on this as well?

If you’re having trouble getting an accurate reading, turn on layers.acceleration.force-enabled=true, WebRender and use Xrender in about:config

Still unsolved as of 435.27.06.

Since nobody posted, I guess nobody uses Freesync with Firefox on Nvidia drivers, so this will remain unfixed forever.