You seem to be saying that you are upset because external devices are not supported for UEFI secure boot. I believe that this is intentional. The concept of secure boot is that the BIOS is certifying to the O/S that a chain of trust exists for all devices. I do not believe that it can make this claim with an external device in the picture; it could be replaced at any time by anybody. You will need to choose whether you want an encapsulated secure system or an open insecure system.
Just my opinion...