This also guarantees they can be paired with eRX FD too right?
Pair one shifter to eRX FD and the other to eTX RD for a widerange 2x setup? The seatpost battery powering just the FD is weird, but that's a setup I want
The RD is the "master" or the system, so it seems to handle the communication, both with the brifters and the FD. This one might not have the ability to control an FD, but I believe someone confirmed the eGR does.
If that's true, then you could do what you want with the new eGR that was announced, now with 50t compatibility.