Interesting, chaps, and you may well be right. However, I am suspicious of the wing flap effects because even on different take-off flap settings, the halt in rotation at 10 degrees is identical. There is no effective downwash when your wheels are still firmly planted on the ground- there is nowhere for the air to go. So if the feeling is the same as you approach 10 degrees nose up for different flap settings and different types, it seems to me it is purely the interaction effect of the tailplane compressing the air as it gets near the ground.
Milt- the effect is quite sudden at 10 degrees. It doesn't appear to build up, just suddenly stop your rotation at 10 degrees. You pull a rotation and leave the stick fixed. The rotation is steady until you get to 8 or 9 degrees when the effect kicks in. With practice on the type you fly, you learn to subconsciously give an extra gentle pull as you approach 10 degrees to overcome it.