See summary
I should mention, those results are with Intel graphics. With AMD graphics the screen just goes all garbled and not blank.
This can be reproduced easily by executing the following command from a gnome terminal window: sudo dnf reinstall glibc
OK I just had the exact same issue on a system running an xorg session doing a glibc update. I am moving this to be a glibc issue. whatever it is doing in the update process that seems to be either hardware or session provider dependent it should not be doing.
*** This bug has been marked as a duplicate of bug 1370136 ***