Can you elaborate on where you're seeing the big peaks in the documents? Almost all the graphs in the 101 documents are Transfer Functions and not Response Charts, and having peaks in those has nothing to do with a flat response.

Actual Response = Transfer Function applied to Raw Driver Response

There are, however, 6 Response Charts in the 101 Lab Handout documents, from pages 26 to 31. Of these six, only the last one on page 31 would represent the response of a PI Speaker, and we do see a flat response from the tweeter +/- 3dB. The other five Response Charts from pages 26 to 30 do not represents the response of a PI Speaker, but rather steps to the final PI crossover.

regards,
Gar.