After looking at various lighting catalogs that would help me collect lighting from around the world, and learning about the various electrical properties of various HID lamps, I have been told by some people that European high pressure sodium lamps are not designed for operation on CWA ballasts. However, when reading a couple of lighting catalogs intended for the Mexican market, I have found that they feature CWA or auto-regulator ballasts that are intended for operating European 70w, 100w, and 150w high pressure sodium lamps as well as ballasts that are intended for operating most North American high intensity discharge lamps including North American 70w S62 high pressure sodium lamps, North American 100w S54 high pressure sodium lamps, and North American 150w S55 high pressure sodium lamps as well.

On page 91 of this Mexican ISB Sola catalog, you can find some listings for CWA ballasts intended for European high pressure sodium lamps:
https://documentcloud.adobe.com/link/review?uri=urn:aaid:scds:US:5694b65b-9dd4-4dc2-8664-127b72d33c50#pageNum=93

On page 65 of this Mexican Philips catalog, there are 2 listings that feature CWA or autoregulator ballasts that are intended for Philips SON-T PIA lamps:
https://documentcloud.adobe.com/link/review?uri=urn:aaid:scds:US:9d861c3f-a4e3-40a3-9b15-f1e459a6f761#pageNum=63

Does anyone think that these CWA ballasts intended for European high pressure sodium lamps have a flawed design?

CWA ballasts can't run European HPS lamps properly, because of their voltage rise during life. They can only run the TCLP compliant HPS lamps and non-cycling HPS lamps, as these don't suffers from voltage rise during life.
Generally speaking, CWA can't withstand the voltage rise during life of regular HPS lamp, since this allows them to run the lamp at dangerously high currents.