I'm able to work around this by manually setting my monitor to their fps cap of 60, but if I leave it at 165hz with freesync on, it'll rapidly swing between 60 and 165, as if it has no idea where to land and adding a noticeable amount of stuttering in the process.
I've only ever seen this noted on random ProtonDB reports and it's just so strange, as it works just fine with every other game I've played, where at the very worst it's just useless. Currently experiencing this on GNOME with x11 on amd hardware, but I've had it happen with other setups as well.
I guess this is a PSA as well. If you have a high refresh rate display, set it directly to 60hz to improve your experience in these games. Normally freesync would make this unnecessary, but that's not the case here.