You're right of course! Capacitors add capacitance... that should have been clearly stated in the nameCapacitors don’t add resistance. In the type of circuit a bass uses you can change the upper frequency characteristics by either decreasing capacitance or increasing resistance in the circuit. So lower value capacitors or higher value pots will brighten up the overall sound.
All I'm saying though, is that if one of the pickups needed to have a darker character, or seem as though they were at a different level, this may take care of it.
I used to have a stacked knob jazz bass, and I always thought that rolling the tone knob off on one of the pickups had more of the effect of one of the pickups sounding less prominent. It sounded less prominent in a different way that backing off the volume of the pickup, but still in the ballpark somewhat. I'm guessing obviously, but I was thinking that sticking a big capacitor in there may be like having a "character" switch.
Personally, I'd still advocate for a push pull pot, but I don't know the make, model, or dimensions of the control cavity.

