My guess is, as part of the script that runs when you activate it in CachyOS Hello, it uses a different method to autostart it.
Details can be found here:
Because CachyOS Hello is desktop environment agnostic, it might be using the systemd service method of autostarting instead of XDG Autostart. If true, then you would need to either disable that service or uninstall the package(as we suggested above).
To quote the GitHub page I just linked:
- Enable the associated systemd service (in case your Desktop Environment doesn’t support XDG Autostart):
systemctl --user enable --now arch-update-tray.service
Emphasis is mine.
However, it is just a guess that this is what’s going on behind the scenes with CachyOS Hello.
I can say the fact that unchecking the Cachy Update box in CachyOS Hello does not sufficiently undo what it does when it is checked is a known issue and it’s probably something that’s in the works to be resolved. I think I remember reading something along those lines but I’m having trouble finding it at the moment.