Actually it is already exists in F40, but I continuously forgot to post it
When I enabled VRR on GNOME, if I enter to full screen mode in some applications (in the video, terminal and game), and some system dialogs triggered (in the video, volume control), including system notification, vol, brightness control, the screen will flash, just like the behavior when manually adjusting refresh rate settings. It is annoying that I need to force the refresh rate to 60Hz to get better battery life.