As I learned from Danny this morning (wow does that guy know a lot about this system .. and is very generous to share it) .. the return signal sent by the RX is transmitted with less power than the transmitter that controls the model .. so the return link will (by design) have lower quality than the uplink.

The idea is that when the downlink (which is what you see on that screen) is bad, you take action to bring the model closer or land, and use the extra transmit power of the uplink as insurance so the model is still under control. Very sensible design, I'd say...

Dave