I would suspect that those angles are a result of mold distortion while the parts were being cast. We'd see that a lot when mold walls were too thin. Then as now, the silicone was really expensive and used sparingly. Plaster mold jackets for relatively small molds like these were rare as they added a lot of labor time. Julien is doing a great job and I appreciate his efforts to replicate the "screen used" castings but personally I prefer straight sides as was probably the design intent. That's the great thing about this hobby, there's room for all kinds of interpretations of the originals.