Reading on I see that there is something called "Half-gain defined Q", which means that the bandwidth calculated from Q is done using 1/2 the gain value, resulting in a symmetric filter.
http://www.tonmeister.ca/main/textbook/intro_to_sound_recordingch7.html#x27-3880006.1.6

So - is the Empegs' filter using this half-gain technique (resulting in symmetric filter) or is is regular Q (and therefore asymmetric)?