It looks like BIOS v3.09 fixed this (BIOS 3.09 Beta release); I just removed the udev file and reran the two commands to undo the changes. Fingers crossed that it works!
(I’m guessing this was the fix: Merge pull request #485 from FrameworkComputer/hx20.keyboard_key_scan… · FrameworkComputer/EmbeddedController@fa89820 · GitHub)