I've had the same experience with Doom (2016). The most irritating thing was the reduced input latency on Linux, which threw me off for the first few hours. After getting used to it I only boot to Windows for UWP games.
It threw them off for the first few hours, as written. Doesn't mean that low latency in general irritates them, just that they weren't used to it at first.
I'm a gamer myself. Upgrading my display makes me slightly off-game myself, until I get used to the new one. Same when getting a new car, where the brakes are way more sensitive than on a old car. Doesn't mean I don't like the brakes to be more sensitive, just means I'm not used to it.
And yes, the first few weeks of sensitive brakes are irritating, just touch the pedal and the car grinds quickly to a full halt. But now I do like it better compared to when you fully press down the pedal and the car slowly stops.
Huh. That's a big competitive advantage in competitive games. Why don't pro CS players use Linux? Is the difference smaller in the games that have been optimized for competitive play?
Most professional CS is played at 4:3 stretched so the PC is pulling in hundreds of FPS
That's unlikely to be true anymore. Even a modestly modern GPU can produce 100's of FPS in CS:GO at 1920x1080 or higher resolutions. Benchmarks for the 3080 were showing 400-500 FPS in CS:GO at 1440p resolutions.
After maybe double your screen refresh rate, all excess FPS don't matter and are effectively wasted. Pro's mostly use 144Hz monitors because 240Hz is indistinguishable[1] - making anything above 288FPS basically a waste (and it's debatable if anything above 144FPS with FreeSync enabled is a waste too).
Personally, I always had the feeling that video was slower on Linux (always used nVidia proprietary drivers in Linux), but when I used to play a bit of e-guitar the audio latency was definitely better in Linux (but as well just for audio there are a lot of settings that play some role - e.g. https://wiki.archlinux.org/index.php/Professional_audio ).