Fedora is now using grub2 with BLS, it makes lots of settings in /etc/default/grub not being used.
The latest way to unhide the grub2 menu is:
sudo grub2-editenv - unset menu_auto_hide
https://discussion.fedoraproject.org/t/how-to-disable-grub2-menu-auto-hide/76519/4?u=sampsonf