Just to close this out, and not be "that guy" (https://xkcd.com/979/), I ended up just rolling the kernel back to the Fedora 35 kernel (5.14.10). Without a good way to isolate where the problem is (between XFS & LVM), I really didn't want to waste time tracking this down, and restoring my system every couple hours. I'll try again in 6 months or so and see if maybe it's been found and fixed.