firstboot asks you to create a new user when running - even if you have configured e.g. yp during install. It shouldn't, in that case you already got plenty of users configured...
The authentication screen in anaconda is going away in the next release, so it's important for this screen to always be shown. I've added a "Network Login" button to the firstboot users screen that will allow you to run authconfig-gtk if you don't want to create local users. Resolving as Rawhide since the latest trees behave as I described.