Interesting. Ok, so there's something else going on here. I'll have access to a T2 system next week, so I'll take a look then. Is this something that started happening recently, or has it always happened if this config option is set on these platforms?
Before https://github.com/torvalds/linux/commit/f5390cd0b43c2e54c7cf5506c7da4a37c5c..., we had to add efi=noruntime to get Linux working on these machines. Now, its this config option only which is the issue.
You may want to follow https://wiki.t2linux.org/ to test on a T2 Mac, since many T2 patches haven't been upstreamed yet.