I’m not downvoting anyone here, but I will say just because you don’t notice, doesn’t mean it doesn’t have an effect.

I have a 7800X3D, 3090, 128GB RAM, NVMe SSD, all tuned and running on a “stripped down” Windows install, and I used some benchmarking scripts for Stellaris and Modded Minecraft that I already used for other stuff. Background churn absolutely affected frame time consistency (hitching) and simulation speed.

I imagine it would be even more dramatic for a game that saturates the whole CPU, like Cyberpunk 2077 or something, though I have not tested that empirically. And this testing was on Windows; certain schedulers on Linux (like CachyOS offers) might handle background churn better, though there will always be a tradeoff.