Rostering is not so dumb either. They often call certain nationalities offering a trip 'home'. If accepted they then swap the originally rostered pilot with the 'accepting' one and give the first pilot another trip.
I know a group of Swedish FO's, all connected on Whatsapp, had this happen. One messaged (at 430am) that rostering was calling asking if they wanted a Stockholm trip so be aware. But in this case ANOTHER Swede in the group already had it rostered and was shocked to see them trying to 'give' it to someone else.