Got the call tonight. I mentioned to the rep about the issue with my niece & her husband's itinerary, but he 1) didn't really care, and 2) was (understandably) unable to do anything about it. The email confirmation I later received shows the new flight (half an hour earlier) is rebooked as WGA. <sad trombone> I assume the AT booking was either something they do to hold the flight temporarily, or just a screw up.

Of course, as expected... (but still very annoying), is this: