Hi Paul
Its not as simple as that makes it sound. A stiffer rod the same weight, length, build would certainly have a higher frequency - you don't have that. Fairly certainly a #10 rod is heavier than a #6. "The same force" looks to me like it's shot through with assumptions - I pick up a #10 and a #6 rod, all else being equal I use more force to lift the #10 - I certainly need to apply more force to move the heavier rod so that I end up with the same line speed. Vary the carry and you vary the frequency as far as I know, the line damps the natural frequency of the rod.
So...maybe ask Merlin ?
Oh and I have no idea what watching loop shapes (on shaky video) and trying to compare them can say about the frequency of rods.
Magnus