I noticed this in the test builds when SubSurf became a modifer the bitwise comparision between the modes and the modes retured from a mesh, broke for subsurfaces. From what I am testing its still seems broken is this correct?
Edit
Seems I did a little print dir() for modes and only NOVNORMALSFLIP TWOSIDED AUTOSMOOTH showed up… but in the 2.41 docs it clear shows
NOVNORMALSFLIP
TWOSIDED
AUTOSMOOTH
SUBSURF
OPTIMAL