I agree with you Dennis, I don't think the peak is intentional. I did not measure it as high as others, but it is there.
This shows it better.
You can see there is something not right in that region. I suspect it is most likely diaphragm related.
I suspect they use an exotic diaphragm for marketing reasons. I'm suspicious of hard domes. I know B & W say it does not break up until an octave above human hearing. I have my suspicions that assertion is not entirely correct.
I know you like ribbons, but to me the SEAS excel Millenium tweeters are the best I have come across. Very flat with excellent dispersion, take a lot of power and sound excellent especially on the high strings.
That looks a lot better than the Diamond tweeter.
I suppose the critics would not be happy with a soft dome. However I think they sound the better and would take that slight high end edge of that Diamond series. They would have to come up with a new name though!