It means that the audio is sampled at 192khz and each sample is 24bit, not that the audio is recorded with hardware capable of recording sounds up to 192KHz
For audio-postprocessing, I might be convinced that there is a benefit of raising the sampling frequency that high, but for pure hi-fi consumers? No way. This is snakeoil.
The argument you should be going with is that the speakers and headphones that people will be playing the music on doesn't do ultrasonic sound.
talk about unconvincing
For simple listening there is no benefit. As you pointed out it ca be beneficial if the audio is processed (for instance, slowed down).