> but it's misleading to label them as travelling at "17,500 mph (28,160 kph)"

Really is? Ground speed is still what I expect and want to read, relative speed to each other at time of rendezvous would also be nice sure.. still, I mean depending on vectors, it may be over- or underestimating almost the same.. and I claim ground speed is what most people would expect. As someone said, the chance that their rendezvous speed is magnitudes off is slim.