Turnaround times are undoubtedly manipulated by operators to make schedules fit particularly with regard to flight duty times. But it is a two edged sword. If the turnaround is not regularly achievable then it will cause problems elsewhere for example with slots etc. We had flights with 25 minute turnarounds that could be achieved, just! Equally we have other flights with 45 minute turnarounds which are almost impossible to achieve. So it depends.