Here I have the two default returns...A has reverb it, B has simple delay. Here is a snapshot of drum racks.

Under "Audio To" shouldn't you be allowed to select A or B from the menu?
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Here is another screen shot of the Drum Racks return window after I drop a chorus into the Drum Racks return.

Now my question is why does it now suddenly enable you to have access to sends A or B now after I dragged a effect on the Drum Racks return? I can even delete the effect I just dropped and still get access to the returns from the session view.
Im trying to figure out if this is a bug or normal behavior...can anyone confirm it as a bug or make sense of it?
Also sorry for the large screen shots.