The treble peak is near 14kHz, where people's hearing starts to drop off massively. Humans don't have good resolving power or pitch identification up there anyways, so it's not harmful. That 14kHz peak is a good reason why the HE400 has good air. The
FR/CSD differences are not huge, but the velour pads seem to indicate overall smoother response (less dip in upper mids, more gradual peak in treble, more gradual transition from bass to the upper mid recess). First plot is with the pleather. The second plot is with the velour pads.
I haven't heard them with the velours yet to confirm with my ears, but given the number of people who say that it works, and these measurements, it's a high probably that the velour pads do work.