What you are seeing on a timetable is the block time, not the flight time.

Flight time for MAN is usually 30-35 minutes. It is quite normal to allow say 15-20 minutes from push back to takeoff, and say 10 minutes from landing to getting on to a stand. And they may want to add in 5-10 minutes for a flight at a busier time of day to allow for some holding before the approach. As far as I remember MAN has always been timetabled at somewhere between 1 hour and 1 hour 10 minutes depending on specific flight so I don't see any cynical approach here. Timetabling that route for anything less than an hour would be quite silly on BA's part.