The SCPB Antiquity has even poles.
It sounds like SCPB Antiquity II your friend has. They have raised A and D poles but the A is raised more, like the original pickup in my '56. Designed to follow the fretboard radius and the string response is very even in my '56.
My 69 Telecaster Bass had an Antiguity II in it when I got it. I didn't notice an appreciable uneveness in string response. What is the fretboard radius of the neck he is using it with? Maybe it is really flat?
What I did notice about the Antiquity II was it sounded just aweful as far as I was concerned. Thin, nasal and an over the top initial spike in attack. I swapped it out for a SD SCPB Quarter Pounder. Much better sounding pickup to my ears. Currently installing Jess Loureiro split coil 51 in the Telecaster Bass with push pull pot to allow it go series or parallel.
BTW. Here's a shot of what Carlo is saying about the 57 split. My 82 Fullerton 57 RI.