Yes, I would call this fairly frequent. In recent years, BA has become ruthless when it comes to taking out occasional frequencies if it feels that it doesn't have the numbers to make all flights sufficiently profitable. One MIA rotation is taken off for the winter despite this being a very popular destination at that time of the year, virtually all European destinations have a "Swiss cheese" schedule with the odd rotation cancelled sometimes as a one off or at times more regularly. Doing it early, the cost for BA is minimal and that helps them improve yield significantly.