Not so much anymore (I believe they updated it) but originally they didn't allow kernel modules.... I believe they are adding module support now/soon.

This mattered for me because I wanted to remap esc/caps and to do so would have required a module. I tried everything I could with xev/xmodmap (and I think even keyd, which was the thing that required the module). xmodmap won't work due to how windows interfaces with WSL input IIRC. So without module support I wouldn't be able to use keyd (again, IIRC, it's been a while).

I just know that without module support I was unable to remap keys in the console (perhaps in GUI mode it could have worked, but I'm not using GUI).

I ended up using PowerToys to remap globally/inside windows and it's fine, but it wasn't my preferred method. I can't recall if systemd mattered or not, but in my case I didn't want to use systemd. Perhaps it wouldn't have been an issue, but yeah.

Recompiling with module support was the only way I would have been able to do that at that time.