Thank you for this thoughtful response, Siegfried. I'll just add a few notes. One is that recommended dosing for indomethacin is all over the place, between 50mg/day and 300mg/day. And while some sources say the effects if indo can be seen pretty quickly, others say it can be a couple of weeks or more. So I can't help but wonder how many people have "tried" indomethacin but (as is also true with some CH meds like verapamil), not really had it at high enough doses for a long enough time for a fair test. Second, I would be cautious about any data regarding hemicranias, just as we have had to be cautious about CH data. Hemicrania wasn't recognized as a medical condition until the 1980s, and I'm going to guess that the majority of doctors don't recognize it, so it can be strongly underreported. I wonder sometimes how many cases of "intractable chronic CH" are actually misdiagnosed hemicranias. There was a journal article in 2001 with the title "Hemicrania is not that rare." One of the authors was the great student of CH, Todd Rozen. (https://www.ncbi.nlm.nih.gov/pubmed/11577748). Maybe current projections factor in that observation. Also, the women/men thing is highly untrustworthy in my view, because as we have seen with shifting CH "statistics" over the years, women quite often get misdiagnosed. Even though the hemicrania reports go in the opposite direction (more women than men with hemis; more men than women with CH), I just don't trust any gender-related statistics since there's no reason that I know of that there should be a prevalence in either direction, and so I tend to think it's a function of some kind of diagnostic error.
All that said, your general principle is probably correct, and maybe people should treat things as CH unless standard CH abortives don't work for them. (On the other hand, there are some "experts" who say no harm done with first trying indomethacin so hemicrania can be ruled out.)