My, probably wrong, information is that the information is passed at the last minute. Like two or three days - to avoid owners letting privately and so that Thomson can do late offers.
This is particularly bad news for owners at the end of the season, because they don't want to have to stay open for one or two guests. Come mid-October they've had enough. There was a jolly atmosphere in the village last year when they could close a week earlier than the theoretical end of season! Happy owners dispensed free drinks, and happy reps packed their bags and headed home.