Aha!
So... series vs. parallel, as we were discussing a few days ago.
My early SUB (2003) is wired in series.
A couple others I have seen, both 2003, were wired in series too.
All active.
Being early, the logo just said S.U.B.
My SUB5, late 2004, was wired in parallel.
I assumed 4 strings were series and 5 strings parallel.
Now, my new SUB, the purpleish "red wine vomit"... I don't know whether it's a 2005 or 2006. Previous owner removed the label with the serial number, but it has the compensated nut the headstock says "SUB Bass" (and no periods between letters", so it's definitely a late one, probably 2006.
Well, I removed the strings to clean it all well and opened it up... and it's wired in parallel!
So maybe they started out with series wiring and continued with parallel? At least the 4 string versions.