The guitarists' general description sounds accurate to me. A guitar sound with a lot of low mids may muddy up with a P bass, but this depends also on the P-bass pickup, its electronics, string type, and tone knob position.
If this is a prelude to working with a guitarist that will not compromise on tone or frequency space, I'd take it as a yellow flag. Especially if I didn't own a jazz bass already, which I don't.
A professional guitarist will make the necessary adjustments without controversy or drama, and still get "their sound". As will a bassist. But merely stating a preference is ok with me. It is interesting though how that shoe is never on the other foot. How many bassists tell their guitarists not to play humbuckers, because you prefer a single coil tone from the other musician? That pretty much never happens.
As long as its a conversation between adults, it shouldn't be the prelude to a problem.