If you want to implement UEFI secure boot and verify existing signed objects then you need to incorporate Microsoft-issued certificates into your firmware, but that's very different from needing Microsoft to be in the loop - the certificates are public, you can download them and stick them in anything.
Already today you can remove the Microsoft keys from most mein board's UEFI and enroll your own. You can perfectly make your own UEFI implementation without Microsoft.
Except that many component manufacturers release their efi capsules signed with Microsoft PKI. So no, you can't fully remove them if you want to verify updates.
While "So no, you can't fully remove them if you want to verify updates" is a valid point, it's also an answer to a different question than the one asked.
Looking at the members on the repository this seems to be a Microsoft project?
As far as I remmeber, they control the issuance of keys for bootloaders. Or is this project supposed to do away with that?
https://microsoft.github.io/mu/
Mu has some bits & pieces of Rust code and EDKII is still the upstream for Mu.
Patina is 100% Rust DXE Core implemented from spec.
[0] https://github.com/OpenDevicePartnership/patina-qemu
[1] https://github.com/OpenDevicePartnership/patina-dxe-core-qem...