On the latest version, I'm seeing surfaces and breps in wireframe view, although I've got shaded view checked in GH (and Rhino for that matter). I see it work right sometimes and not others. A bug?
I also came across this case once, but it was only for one very complicated brep (with over 250 OnBrepFaces).. all other 'simpler' surfaces were showing as shaded along with this one in wireframe. However, when I baked it, Rhino displayed it correctly so I just lived with it as long as my end product was okay.
It probably is a bug but I am not sure if it can be attributed to this particular version. And it seemed to fail only for super heavy Breps..