If Engine "B" is operating on the main line when Engine "A" enters the main line from the auto reverse loop, will Engine "B" change direction or will Engine "B" continue its journey?
With DCC, the reversing of locomotive direction takes place within the locomotive, and only when it is commanded to do so. If you grew up in a DC model railroad world, it's easy to forget this feature of DCC.
When Engine "A" transits the reversing section and returns to the mainline, any "change" will have been to coordinate the track polarity of the DCC track current present on both the mainline and within the reverse loop. In other words, when Engine "A" returns, nothing changes for Engine "B", or Engine "C" or Engine "D" for that matter. With DCC you are actually running your trains and NOT your track.