> The list of dropped components is quite large. The cryptsetup, cryptenroll, unified kernel images, kernel signing and systemd-boot work nicely together.

These are also all components which would be extremely difficult to make portable - they require tight integration with the kernel and its boot process. I can't imagine how you'd implement them in a portable fashion, short of either making changes to the kernel on one or both operating systems, or implementing a complex set of shims to make them present similar interfaces. Either one of those options would be a sizable project on its own - I can't fault the developer from shying away.