I would also like to mention that this is still affecting 1.18 and 1.18.1 pre1. I think what's going on is that mouse speed is being affected by the frame rate. I don't imagine that being a hard thing to fix
I updated the description to include a youtube video showing the problem.
This is from the creator of the post. I would like to know if progress is being done on this post. The workflow screen just says the last action done was that it was reopened when I added the video. I would also like to mention that I've noticed mouse studders even during high fps, but with lots of chunk loading, so I have a feeling that sensitivity isn't tied to fps, but its tied to chunk loading. Though I mainly noticed this behavior when I was using performance mods like optifine and sodium.