I always found it hard to trust tetrio's fps meter on f8. The easiest noticable fps drop is when the tetrio insider banner appears and causing the game to stutter to like 1 fps and yet f8 fps will not show it.
In general most fps counters fail to work on tetrio for me, tried nvidia, gamebar, rivatuner, etc. But steam's somewhat recent new performance monitor actually worked(need to run game as admin on windows). As shown at the start of the video, it shows the fps tanking when the insider apply now banner appears.
What's then interesting is going in-game. Steam's performance monitor seems to still be showing it cap at 144 fps, when I have it set at 288 fps. Changing the fps cap in config->tetrio desktop did not change things.
Also interesting having it capped at 144 fps or having hard vsync on(and closing reopening game) have both fps somewhat matching.
So I have no idea what's going on, no idea how fps counters work etc, so no idea what I should be trusting to know if im actually getting stuttering.