Genie, I think that it was because the bass player didn't have voice lessons whereby he could have approached his voice as an instrument. Pitch in singing is not always a matter of being able to hear it, but reproduce it.

I think perfect pitch can be acquired. When I first started music, I didn't have perfect pitch but now I'm pretty much able to tune my guitar without referring to a pitch source.

I can recognize pitches from machinery or sometimes train whistles without a pitch source.

I might possibly be a "cent" off but from a practical standpoint, not an important consideration which is easily correctible.

People with perfect pitch might have trouble when dealing with a piece that employs sophisticated modulations or those that employ a 12-tone series. I wonder how much of this is attributable to environmental conditioning as well as genetic potential.