Yes, absolute analog axes are assumed to be centered at 0. It is the OSD's job to ensure that things are calibrated that way.
That's not the behavior I'm seeing in outrun. After fixing the overflow (src/osd/sdl/input.c, line 71, change 8 to 28), OutRun is very playable on a DualShock 3 with -nosixaxis and the pedals mapped analog to pressure sensitive buttons (I recommend L2 and R2). Its input test screen gives exactly the desired values too (00 up, FF down).
-E- Crus'n World (crusnwld) and Ridge Racer (ridgerac) behave in exactly the same way. Are you sure pedals are not an exception or similar?
On a related note, I found another issue. I can't map the button axes through MAME's menus, but if I manually edit ~/.mame/cfg/*.cfg, they work fine.