There are other variables at play. The ease of move can be affected by smoothness of the surface of the props and the internal surface of the fork where the prop goes to. Tiny amount in any of such variation or tiny burr on the internal edge or a bit of finger grease can change the equation. And from experience the force required to move the prop in the fork can vary with angle too. So, what I am trying to say is that feel might be in this instance more reliable indicator of the proper screw tightness than the torque applied to the screw. The same torque might not necessarely result in the same stiffness of the prop in the fork. The only scientific approach would be to measure the force required to move the prop at a specific distance from the pivot screw. But that is a another thing altogether....
The props have 2 teflon washers that act as sliding surface, but yes I agree it would be best to measure at a specific distance from the pivot point. But barring that, the use of a calibrated torque driver works quite nicely, I have used it and it works. Given the fact that the manufacturer are delivering the props with a specific torque already set (although it is to tight) I think it should be fine. What I am after is a torque value that they recommend, so far no sign of response.