My impression having gone to a few live concerts and sitting in an upper balcony is the higher frequencies travel upward whereas bass doesn't. This is also true in the forest canopy where certain species communicate at high frequencies above the tree canopy, low frequencies work closer to the ground.
In the shorter distances of an audio room perhaps this isn't noticed or it could as the poster is alluding to give an illusion of height. But it's really not an illusion because the higher frequencies IMO are travelling upwards. 
Not quite. Higher frequencies are more directional. With live sound systems (line arrays) we aim boxes everywhere in order to get a flatter frequency response to the upper balconies. The lower frequencies travel there, but there are more impediments to the low end being even in a room. Low frequencies are more omni-directional as you go lower, which is the problem because certain places in the room will have phase problems and those frequencies will cancel each other. The high frequencies travel directly there but a lot of the low frequencies are bouncing all over the room and causing problems that are pretty much impossible to solve in arenas and other indoor venues.
The illusion of height in this case is caused by how the sound system is deployed. But again, there is no function on a mixing console that places some instruments higher than others. Well, that's not totally true, but the system that does it is still mostly in beta test form and rarely used because of it's complexity. It's called L-isa and it's made by L-Acoustics.
