I don't think I am wrong, if they were standard 5 string PUs, they would have 10 poles (2 per string) not the 9 that these PUs have.
assuming these are the J-45 pick-ups (and I'm not aware of any other equally spaced 9 pole Jazz pu, correct me if I am wrong) the website that I linked above lists the dimensions as:
Neck: Bridge:
Width: 0.73" Width: 0.73"
Length: 3.55" Length: 3.71"
Depth: 0.83" Depth: 0.83"
Which are pretty close to the standard 4 string Jazz PU size.
Also from the site:
The J-45 set offers Bill's multi-pole piece system for 4 string, 5 and some narrow 6 string Jazz Bass instruments. His airgap noisefree design for the jazz bass replacement comes standard with pole pieces at a slight stagger to accommodate most neck radius. Flush pole pieces are available per request which may require additional wait time.