EBBR reqfers to chapter 2.6 "Requirements" of the UEFI spec if no special exceptions are provided.
The UEFI spec requires to support HII resources in the LoadImage() boot service. If an image contains a HII resource it has to install the EFI_HII_PACKAGE_LIST_PROTOCOL on the image handle. But chapter 2.6 does not generally require support for HII protocols.
It would be helpful to clarify if supporting HII resources in the LoadImage() boot service is required to be EBBR compliant. I would prefer EBBR not to require this as it adds a lot of complexity to the firmware.
The UEFI spec further requires supporting loading images via the EFI_LOAD_FILE_PROTOCOL and the EFI_LOAD_FILE2_PROTOCOL. This might also be a candidate for skipping in the EBBR.
Best regards
Heinrich Schuchardt