From what I've seen, even though Dish parks fifteen or so HD RSNs on 129tp8, only four can carry games there simultaneously. If there are more than four games, the overflow moves to some other transponder for that day. Dish doesn't have enough transponder space to show all the RSNs in HD all day, so they only show the games.
The logo and music that you see is going out at a pretty low bitrate, compared to the HD games.
Huh, didn't think that few would be broadcasting at the same time, but now it makes sense. Thanks for the info!