Okay, and I see from Gibson's website that the SG bass is 1.6" (40.64 mm).
Meanwhile, the American Standard Precision (my personal reference for a P), is 1.625" (41.3 mm). I'd never really thought of my SG bass as having a P-like (P-lite?) width, but I guess it does.
It's funny, I'm totally comfortable with the necks on my two Ps (American Standard and Mexican Standard, both thin from front to back). But whenever I play my Jazz, I like the neck even better!
Now, the wider and/or fatter front to back vintage style Ps necks are of no interest to me, but a "regular" (for me) thin 1.625" P neck is good. Kinda a weird shape though, with that thin front-to-back aspect.
I really like the SG bass neck - more normally rounded in the back than a P, but with P-like width, but just a bit narrower which is nice. Add in the shorter stretch between frets than a P and I'm very happy. I'm a bit curious to try an Epi EB-0 now though