Yamaha BBG4AII - what do these knobs do?

Before you start berating me for my ignorance, here's the actual question:

I've been playing this bass for about 4 - 5 years now, and I've always gotten the impression that the knobs were volume, bass EQ, treble EQ and pickup blend. However, I read a couple of reviews of the bass today that said it had a 3 band bass-mid-treble EQ and a volume knob.

My question is this: Are they right, and if so, why would someone build a 2-pickup bass without the capacity to blend the signals to your liking?

 

Bumped, so someone might answer.