Anaconda's current logic for dealing with EFI installs effectively precludes you from installing more than one copy of Fedora to a single system via EFI unless you fiddle things manually. Anaconda wants to create an EFI boot manager entry named 'Fedora' when you install by EFI. If it finds a pre-existing 'Fedora' entry it just silently wipes it and creates a new one pointing to the Fedora installation that's now going on. There's no option to have two entries in the EFI boot manager, one for each Fedora install, or anything like this. The only way to do it would be to manually rename the existing entry (via efibootmgr) before doing the second Fedora install.
Not a scenario we're going to support.
I predict some complaints from people once they realize they won't be able to dual-boot a stable and a Rawhide install on an EFI system...
People can still use the grub menu to load other OS's ... unless the new EFI "security" mechanism prevents it.
Is EFI an option we can choose not to use? If our machines do not use EFI will anaconda use grub2 (I think it would have to)?
(In reply to comment #4) anaconda will use efi if it was booted with efi - and bios if it was booted with bios. grub2 will be used in both cases ... but the hardcoded efi paths are obviously only used for efi. Note also that grub2 upstream support custom bootloader ids - it is fedoras own decision to ship pre-built (and signed) boot loaders with hardcoded bootloader ids.