[easton]

A platform for amateur XNU kernel research was required, since the only other one besides the Mac is the Security Research iPhone (which is specifically not for amateurs). All of Apple’s documentation (of which there is little) and the boot loader design itself (what with the blessing process for a secondary drive being to install a tiny XNU partition with the bootloader app), point to the process being specifically designed for loading different versions of macOS. Any ability to install Linux (or Windows) is at this point coincidental.

[notaplumber]

Perhaps that's true. From what I read it shipped in a non-working state (manuals were there, but not some utilities were not), and I recall Apple engineers came out on Twitter saying it was being worked on and included it post-launch in macOS betas, even incorporating feedback. I believe Apple did tease at least Windows, maybe Linux in marketing, but I could be mistaken..

Either way, going after OS developers would be an extremely bad look for Apple, especially when they could just as easily disable the feature, or not have bothered finishing the implementation (or done it completely differently) after news of the Linux porting efforts started to spread (especially the Corellium public demo running Ubuntu).