I'm with
@Asgard ... I think you are going to see similar results for the two prop's due to the play in the hub hinges. If you were to also support the prop in the centre, and apply the pressure half way along the blade, I think you'd see a lot more difference in how much pressure is needed to deform the CF blade.
I also think that the type of testing you are doing is not so significant (and I'm not saying that it's not valuable!). While it does test how stiff the prop is overall, it's not testing the 'torsional' stiffness. That's the stiffness that you feel if you grabbed the tip of the rotor between thumb and forefinger, and rotated your wrist left & right. It's this movement in what aeronautical engineers refer to as '
the feathering plane of motion' that changes the way the prop acts as it spins through the air. Since the prop has an angle of attack to the air, it produces a pressure underneath that tends to push upward on the trailing edge of the prop'. If the prop has little stiffness, then this pressure can make the [or a good proportion of the] prop blade twist to be parallel to the airflow that it's in. When it does that, it loses lift & thrust. However, it also looses drag (becomes more aerodynamically efficient), and therefore becomes easier for the motor to spin. The overall effect is that a prop with poor torsional stiffness tends to provide thrust more toward the hub as it gains speed, with the outer extremities of the prop blades reducing their contribution as they 'feather' in the high-speed airflow. In other words, it's not as efficient as a prop that holds its shape and angle of attack all the way along it's length, at all rotational speeds. It's for this reason that the [stiffer] CF prop's will keep the Mavic in the hover at lower motor rpm's.
If you want to get really scientific ...
https://apps.dtic.mil/dtic/tr/fulltext/u2/a403707.pdf [definitely not bed-time reading!!]
