"The timing of schedule filing is the sole prerogative of each specific airline, so it is rather irrelevant what some other airline does (or does not do). Some airlines always publish schedules for the maximum possible period (and then issue a high number of schedule changes), while others prefer to wait until things are more firm."

Just like it is rather irrelevant that IATA publishes official seasons when airlines, to your point, can publish schedules to whatever extent they wish. All I'm saying is that SU is rather quaint in their lack of putting out a schedule following the end of IATA NH Summer season....