I had this issue last year when upgrading our iMacs to Mojave.
I push the installer package through Jamf, then use the following in a policy under Files and Processes: "/Applications/Install macOS Catalina.app/Contents/Resources/startosinstall" --agreetolicense --forcequitapps --nointeraction
After the upgrade seemingly completes, and the login window appears with the Catalina desktop, I log in with ANY account and the screen goes black and shows a message saying 10 minutes remaining. After that ANYONE can login.
It's HUGELY frustrating. :-) I haven't been able to find a reason for this or a solution.
In some cases I've noticed a time element is involved, so that if no one logs in for a day after the "first" installation, then anyone can login without the added "10 minutes remaing."
