That is just a photoshopped version of the 9.3.1 GP model. A lot changed in the arcpy module, enough that I would consider following that diagram a bad idea.
While I wouldn't call it documentation exactly, the Python auto-complete function is pretty helpful to give you an idea of what's available in terms of methods and properties - even tool syntax.
Besides, why would anyone want an easy to use reference document that, say, you could print and "look at"?
I think many (all?) of us are really rooting for ESRI to change their minds and publish an arcpy OMD for v10.1.