Almost T-Joint/Star-Joint how would you model this?

The SubD implementations inside CAD apps are usually not polygon based. Hence you do not get a facetted model. What you see e.g. in Gijs’s screenshot is the control-polygon (cage) which also exists in any super duper surface model.

I still see a lot of issues with Nurbs-compatible SubD for precise, complex models with cutouts and exact dimensions – but for isolated shape-transitions limit surface based SubD should work quite nicely. Did I already say that the result is not polygons? Ah yes, here :o)