Blue, this feature in combination with ALEMBIC's low impedance pickups allows you to adjust the pickup output separately from their tone.
In general, on most guitars, you relatively adjust the pickups' output by raising them closer to the strings (louder) or lowering them further into the body (less output). With high impedance pickups (no battery, though not always true) like Fenders, for instance, as you raise them closer to the strings, the output rises, but so does your high frequency response at the price of low end. They can get noisier as well. But that's the only control you have over the relative outputs.
With low impedance pickups (your MXY's, as well as EMG or Barts and more), you just get more tone without that spike as you raise them. So you can fine tune your tone, pickup at a time, THEN set your output gain for each. You can really fine tune the blend, set one way louder than the other, whatever you want, apart from the tone of each. Think of them as a two-channel mixer.
I have a five-string Elan with P/J Alembic Activator pickups. The P is virtually flush with the body, the J is way up high, but with the preamp gains I get just the blend I want.
Like the Guinness commercial, BRILLIANT !
PS, be sure and read the post about how to adjust your pickups in the FAQ section of the Club.
J o e y