Yes, it is normal.
The font changes are not system wide since the overlays that changes fonts work like that. I was only able to force Google Sans as default system wide, instead of Roboto font, since I actually replace the Roboto font files with Google Sans files inside the module. Every other font is just an overlay that don't actually change the font everywhere. It's standard procedure for all default font overlays (the ones you have even without my module installed).
With CFI module (Custom Font Instaler) it changes almost all phone texts (except some webs and the chat titles on telegram)