So I tried to reproduce jsedlak's failure of https://fedoraproject.org/wiki/QA:Testcase_dualboot_with_windows%C2%A0on UEFI, but I could not. Here's what I did:
1. Installed Windows 10 clean to a UEFI KVM with 20GiB disk 2. Installed from the RC-1.2 Workstation live, resizing the Windows partition to 13.3GiB 3. Powered off the VM and disconnected the ISO 4. Powered on the VM
I got to a grub menu with Fedora and Windows boot options, and both of them work properly.