How HFTs and other miniature tuning devices might work?

After living with some SR HFT room tuning devices for about a month now, I only know one thing for sure. They work. Specifically, they seem to work by improving image specificity, which flows on to other areas such as image size, soundstage dimension and finally subjective tonal balance. 

As I listen, I ponder the question of how and why these devices may be doing what they do. I have come up with an answer but it's only speculation. Could it be that...

The sound waves projected from the back of speakers (in my case ML electrostatics) are normally reflecting off the back wall, and then returning to the listener's ears at the listening position. The highest frequencies are the most directional, and they are the frequencies which the listener uses to focus on, as the source of the sound. Normally these highest frequencies would be reflecting off many "spot sources" on the wall behind the speskers.

If a device were placed on the wall which synthesized even higher frequencies from the highest frequencies, then those ultra-high frequencies would become the most directional ones. The mind's focus would then be on the position of that single device, as the source of the sound. Could it be that high frequencies entering the HFT (or similar device) are divided (or dithered) into ultra-high frequencies (perhaps by a grid or mesh), and then projected out of the device, amplified by its horn-like structure? The effect would be to make one "spot source" (the highest frequency source) the focus of attention, rather than many spot sources. All lower frequencies would subjectively appear to originate from the same point source, based upon the detection of the source of the ultra-directional highest frequencies. In that way, the tiny devices could influence image placement and soundstage dimensions.