Yes, it is a little ridiculous as far as audible sounds being reproduced. The key thing here is that the resonance frequency of the diamond material is so high that it will not cause any resonance/ringing/distortion down in the audible range (like 20-30khz). If I remember right, the resonance frequency of the Accuton was somewhere around 72Khz, which means that the high frequencies that you will actually hear will be ultra-clean without any tweeter breakup.
If I remember right, the resonance of Beryllium is somewhere in the 45 KHz area. Resonance of metal dome (like titanium dome tweeters) are somewhere between 22khz and 30khz. When resonance happens so close to audible ranges, the tweeter itself will start to flex and distort. This can come across and very bright/harsh sounds. You can hear this on a lot of metal dome tweeters (Focal is an example here - the older metal dome tweeters).
This video gives you an idea of what happens during tweeter breakup/flex:
https://www.youtube.com/watch?v=seNODFTj7TI
I think the fact that the diamond material is so stiff that it can actually reproduce up to 100khz. Not that it matters at 100khz. It’s more important that it is reproducing the 20-40khz area with no breakup/distortion.