I've spied maids composting as well, and I most definitely do NOT have a hack that would cause this. Maybe it was just a fluke, though?
Maybe a path issue -- I seem to recall (before I got the hack we talked about earlier) that if the compost bin was in the maid's path to the trashcan (i.e., right by the front door), the maid would compost instead of schlepping all the way out to the trashcan.