TPL200 higher distortion than TPL150?

According to the Beyma datasheets, and accounting for the slightly higher efficiency of the TPL200, it seems to have about 5 dB higher 3rd harmonic than its smaller brother across the usable band, and also about 5 dB higher 2nd harmonic between 3 and 6 kHz until the TPL150 catches up.

Has anyone performed measurements of these two drivers or is aware of a report or magazine that has tested both under identical conditions that confirms this?

If true, is this due to the x-bow technology - whatever that is supposed to be - that only the TPL200 has?