Yea, this is the weird part for me. Di2 shifters are just buttons. Unless I’m wrong, I don’t see how the signal from a TT shifter would be different than a road shifter. So the fact that they can allow the older TT shifter to shift 12s with a software/firmware update would make me think they can do it with the road shifter. Just use the adaptor as in the diagram and update firmware.