alright. DX11 vs DX10 is not the answer. However, I tested some plane designs with a friend, and found something very interesting.
This plane breakdances (bounces around on the ground after loading in on runway without pressing any buttons)
This plane does not breakdance (this one can take off and land)
The only difference between these two planes is the location of tail fin(s).
So. It seems to have something to do with the tail fin in addition to the wheels.
Another important note is that if the outer wheels' Damper Strength is reduced to 0.5, it does not breakdance. All of this is true with or without the inner wheels. Those are just there for added strength when landing.
Last, my friend tried these with the FAR mod. They both breakdanced with that mod, although the one with the middle fin breakdanced significantly more. And likewise, they both stopped breakdancing with Damper Strength at 0.5