Genuine stereo with different strings going different directions is sh*t.
Unless you are Michael Manring or Victor Wooten, both of whom have done it.
Then there are 2 output basses like Ricky's, some alembics and the Yamaha Attitude. These are not stereo basses - these are for splitting the signal to apply FX to different parts. So on the Attitude (as I'm familiar with them) the big chunky neck pickup gets EQ'd for super deep sounds and into 1 amp.... and the Precision pickup gets a more middy and trebly sound and all the distortion you want into a separate amp. Both signals are run at the same time, so no matter what FX you load onto the mids and highs the lows always stay super deep and clear.
That signal splitting routine is done an awful lot even if a bass only has 1 output. It can be done on a pedal board / in a rack as well (but with no individual control of pickup volume without adding vol pedals etc). This is in no way a gimmick and sounds absolutely massive to the point where every band I've been in with a rig like that has decided against the continuing employment of the rhythm guitarist!