long neck?

Now, why would you think that? The neck is effectively double-thickness near the seatpost clamp, due to the seat post being inside the neck at that point.

Furthermore, the axis of rotation for any forces applied to the seat would be where the neck meets the frame, just above the tire.

There is much evidence that illustrates this phenomenon, and not much, if any, that supports your claim.

So, can you explain your theory? There may be some merit to it, after all…