That speculation cannot be disproved, but with my line source speakers there is no height with the sound stage. The stage expands laterally from both speakers due to phase interactions. This also might explain the sound source coming from behind the listener, in a room where all four walls are completely insulated.
There is a lot of neurological processing regarding phase reception given the fact that the 1D axis of two ears yields 3D hearing so I would look more to that as an explanation.