VeloDog, you're quoting at least 4 year old specs from a discontinued previous model? Seriously?
I'm talking about two I have played personally, both current models. Both the Standard and the Special definitely had Corian. Both had two-piece bodies.
Gibson's current published specs for the 2014 SG Special Bass and the 2015 SG Standard Bass say the nut is TekToid™. Gibson appears to have gone to this for its whole regular USA lineup. According to
this, it's a kind of graphite.
Gibson has used three- and four-piece bodies in the past. In the early 00s, I saw a number of LP Studios that clearly had 4-piece backs. But I see no evidence that the SG Standard basses have commonly had more than two pieces.
Specs change, hopefully for the better.