I don't think the output can be identical to the Cube's digital out, because the digital out on Cube doesn't carry sound... and there is no second port for sound on the Rev prototype. It could always be added later, I guess.
But I don't see it as a sign for worry. It's proprietary. It can be made to support all outputs, like the 360's port. It's more cost effective that way. You just use the correct wire accessory for your setup.
The controller positioning bar doesn't seem to have a port either, unless it go into one of the USB slots.