I think you may have missed what was being asked? I think they assume that an LVM PV is encrypted and could contain the block filesystem and swap volumes as LVs. There is already a boot-time process to unlock such an LVM setup. Why should the swap require a separate encryption key?
As a Fedora user, this is how my disks have been setup for many years, and I don't understand why Fedora have disabled hibernation. During wake from hibernation, the kernel and boot ramdisk would need user input to unlock the PV and to decode the LVs. Then, the hibernation state would be visible at the same time as the other filesystem state, and the kernel could decide whether to load the hibernation image or continue a normal boot sequence.
This seems to provide the protection of content needed for theft of a hibernated machine. I don't know whether there is some unhappy sequencing flaw in the dracut-generated ramdisk (between when the wake-versus-boot decision has to be made and the LVM decryption is done), or, whether someone at Fedora has decided that the threat model is different than we discuss above?
