I think that probably answers my question. There is a raw memory space for efivars that is accessible by the kernel but might also be under control of lower-lev

I think that probably answers my question. There is a raw memory space for efivars that is accessible by the kernel but might also be under control of lower-level runtime services. If that is truly the case then I agree with you, the kernel should default to using the efi runtime to modify the efivars.