"pan Biab so the Bass and Drum parts are L and everything else is R."
Just to clarify; your L/R channels are essentially summed to mono at the mixer output to your speakers because each mixer channels' "Pan" (or balance) knob is centered. I don't think anyone is recommending your left speaker be bass and drums and your right speaker be all else. That would probably not be the sound effect you want to achieve.
The panning recommended is the actual BIAB tracks left and right adjustment. Example; pan your mono bass and mono drum track to the left so it only comes out the left output of your sound card or interface. This allows quick low frequency volume adjustments at the PA/mixer in a live and often solo performance.

Does the noise in your head bother me ?