The How to reset the root password in Rescue Mode section of the document seems to be outdated from a SELinux point of view.

After performing the steps described, the restore of the SELinux context and permissions (step 7) apparently does not take effect, the result being that after reboot, the user is taken to the login screen, but the password is not accepted, probably because of wrong SELinux permissions (as a result of the /etc/shadow file being altered?).

The issue can be solved by rebooting after step 7 and temporarily setting SELinux permissions to permissive, i.e. editing the boot entry and adding the kernel argument enforcing=0. This step might also operate upon the autorelabeling (someone more knowledgeable needs to confirm), since a new reboot, without modifying the boot entry this time, and a subsequent user login, are successful.