I think a lot of how people perceive movement and what they do to reduce it depends a lot on the length of the TT, it's weight, axle ratings (spring strength) and the frame design. There are some frames on ultra-lites now that flex a lot vertically and they need to be firmly planted to the ground front and rear. (I know because we've seen it firsthand.)
Our old 20' TT had hardly any movement with just scissor jacks. Our 29' 2013 KZ TT bobs around like a duck in water with the elec. stab. jacks down. It almost makes you seasick in comparison to our old TT, even with jacks at the axles. The only way I can see to resolve it is to install triangulated cross-bracing. Our new 2014 KZ TT is the same model but with a heavy duty frame. It will be very interesting to see what the difference in movement is. DW has had to deal with vertigo for a few years and has had enough trouble with the world spinning around so would prefer to have the TT rock solid.
I can definitely see why some don't have much of a problem with movement while others have a lot of trouble with it.