It is very true
Way hi fi fans test it is to play a test record..most of us can't hear 15khz or above but we know it is there. Same with low frequency.
Tech person test it using audio signal generator..same result.
Unlikely we feel the presence of 20khz or higher, rats could..hehe
For a Taiwanese made super tweeter, it is not cheap at all. No hi end users will look at them...waste of time to have a demo...lol..They are nowhere near that kinda market. Average folks don't even know what that is..
Typical super tweeter don't need power to drive. Most of the super tweeter max power handling is less than 30 watts RMS. A low price receiver would drive it fine..