The Radiance BSDFs in OpenStudio were computed for the shading devices themselves (e.g. Venetian blind), and do not include any glazing. The BSDF is "applied" to a proxy surface that is automatically generated by the Radiance forward translator at runtime, and the proxy surface is fully enclosed about the edges with polygons projected from the window. The depth of the enclosing polygons is user-adjustable, as these can be used to crudely simulate wall thickness in an otherwise infinitely-thin wall construction model.
So yeah, the shade BSDF sits just inboard of the window you add to the model. You can assign whatever construction you want to the window; there is no need to 'blend' the window constructions performance into the BSDF.
This probably should be better documented... =)
P.S. The 'blended glazing + shading system as BSDF' approach was how we initially implemented this support, but we changed tactics because the other way required nearly a hundred BSDFs just to support generic clear single pane glass.