Hi,
This is not Ground Effect or moment change.
It is caused by downwash from the wing/flap
hitting the Horizontal Stabilizer and forcing it up (working agains the rotate).
Closer to the ground the Hstb is, stronger the effect.
We have this in the X-Plane simulator
Could you try to discribe how/when it feels in real?
Have a feeling our XP model is a bit strong on the
effect as well... .
btw, if it was moment change, it would have the
OPOSITE effect and rotate faster since CG is in front of the gear... .
Cheers,
Morten