The theory for super-tweeters goes: Live instruments can produce ultra-sonic harmonics. Even if you can't hear those harmonics they are still creating sound pressure.
I know, from holding a pest repellent close to my ear, that those sound pressures do press on ear drum, painfully. So they may present some sensation. Just as infra-sonic bass can be felt, even if it can't be heard.
That said, where is this ultra-sonic content coming from? Mics in most cases don't pick it up. In an effort to prevent aliasing in the duplication master mix, brick-wall filters are used to remove anything that does make it through. Then, how many receivers/amps will pass those frequencies. I'd like to see an analysis done of the relatively few 96 and 192 kHz releases out there, how many have actual harmonic content above 20 kHz, and not just noise.
As John said, if you like the sound of one tweeter more than another, it's not because it can reproduce ultra-sonics. Although, perhaps in designing it to handle those upper frequencies a better tweeter was produced.
