There's an error with your description: that particular wire-sealed burner design came after the cap sealed one.

You're right...got past the proof reader...

No problem. There is something that I find particularly interesting with those later 200 and 310 W HPS lamps, it's that those who designed them (and their system) did not consider the fact that the smaller lamp/arctube enables a more effective optical control of the emitted light, especially when compared to coated mercury lamps. They just matched the lumen output without any further consideration. I'm sure that a greater energy saving could have been possible (e.g. with 175 W HPS lamps to replace 400 W mercury ones) if the illumination level on the road was the parameter kept constant rather than the source's integral light output. From a lampmaker point of view the objection may have been a too close proximity with existing 150 W HPS lamps in their product lineup. That's understandable, but then it's surprising that no one offered a 175 W HPS ballast to run S66 200 W HPS lamps, the same way they did to boost 1 kW mercury lamps to 1500 W; sodium lamps are very flexible and can be dimmed.