Slightly off topic, but in defence of operators, the student or hirer is charged VDO (ie oil pressure on-oil pressure off) and that is what they log and what instructors paid by the hour are paid for. Now, when doing costings for aircraft with a VDO you can work on about 115 revenue (VDO) hours for 100 maintenance hours.
So if people want to hire our aircraft on airswitch that's fine, but they have to pay 15% more per airswitch hour than they would on VDO. the aeroplane costs the same to operate whatever clock you use.