I think it was a good idea not playing around if install process is active
When changes are made, an “internal reboot/restore” of the system can occur, for example with i3wm also achievable with super+shift+r.
This interrupts running processes, and maybe calamares could not handle this.
I don’t know if a bug report in calamares git will cause a change, but you can try.
Since I am not a programmer and should be completely wrong with this, you (developer) could alternatively point it out before starting calamares.
Sample:
“Use the coming time during the installation for physical training, the weaker your PC is, the stronger your body will become. However, do not play around with the desktop environment under any circumstances.”