well I can tell you from experience that the difference in spinning a prop or a rotor in regards the start has nothing to do with it. Once while troubleshooting a vibration in a 212, maintenance disconnected the drive shaft and had me start the engines. I was very concerned that with no drag on the engine it would be some sort of crazy start and possibly over speed. Well to my surprise the start was exactly the same as with the transmission connected. Uneventful.
FYI: Not quite. Had you tried a manual start on the disconnected 212 it would have been a bit more interesting vs an auto start which schedules fuel based on RPMs and not load. Airplane PT6As don't have a true auto FCU like the PT6Ts. So the start sequence has more "manual" inputs during a normal start which happens at a quicker rate than the 212 PT6T start. And while some PT6As do have a manual emergency FCU lever, there is no real comparison on the start sequencing between the two models until the fuel hits the nozzles.
