The os prober thing is tricky to catch, it’s a small hidden thing, and difficult to find in the wiki until you found it.
Edits: I am working on a dual boot now installed xfce yesterday. There was no os-prober installed and the GRUB_DISABLE_OS_PROBER=false was not set to false out of the box. Just FYI. Fixing that to show windows in my grub menu.