Only ~15% of people with a pre-2017 diagnosis of hEDS met the newer 2017 diagnostic criteria so the new criteria was a strengthening of thresholds. It's assumed within the patient community is that this was done to ensure that hEDS remained a rare disease. The rare disease classification is required for many NIH grants. The NIH rare disease threshold is (60/100,000) and even a (1/500 or 200/100,000) would cause hEDS to lose this status. The 2017 criteria has been a source of controversy. There has been a fair amount of research since then, e.g. https://bmjopen.bmj.com/content/9/11/e031365. But if there is one thing I don't trust doctors with (or medical researchers with) it's statistics.

The main thing I focus on is the lack of the distinction between hEDS and HSD, there appears to only be a weak association to severity with everything else about it being entirely proportional to the severity. I.e. both conditions appear to be the same thing. There is just so much randomness between individual doctors, and even within the same doctor, that even the severity link is very weak. US doctors especially are reluctant to diagnose with hEDS because of the presumed rarity but also a diagnosis of hEDS can apparently screw up the clients insurance - and as there is no known treatment they don't see the point of doing that. So while it's generally accepted that hEDS is 1/5,000 and HSD is 1/600 I don't see a difference between hEDS and HSD so it all goes into the hEDS bucket. Especially when doctors are also bad at diagnosing the hEDS comorbidities and without those they generally assume they're seeing a presentation of benign hypermobility.

The other thing I focus on is the strong predisposition to Long Covid by those with hEDS/HSD. Dr. Jessica Eccles is doing great research here and if anyone in the medical community is going to find out what I have seen it will be her. Dr. Jessica Eccles has a psychiatry background and which helps her use the psychiatric comorbidities of hEDS to find associations that would not be clear if only using standard diagnostic criteria. Her claims are not as strong as mine but she does have to work within the medical community and can only push so hard, even still her claims are pretty strong and she does provide the evidence for them. She is getting published. I expect her claims to get stronger once she is able to collect more evidence. She is currently using Generalized Joint Hypermobility https://bmjpublichealth.bmj.com/content/2/1/e000478 but notes that the distinction between GJM, HSD, and hEDS is rather blurry and I think in time, when she has more evidence, she will start to challenge the standard diagnostic criteria more forcefully.

As for my own research, I did an unofficial study on the patients of a Long Covid clinic and found that 30% have hEDS/HSD which would be statically impossible if hEDS/HSD was at 1/500 and could only happen if the true incidence rate was closer to 1/50. It's reasonable to expect some sampling criteria basis in sampling from a clinic and not the general population but in testing for such bias I was only able to find a weak effect and nothing anywhere near close to the measured 10x.

So yes, I do believe that the hEDS connective tissue disorder is the unifying diagnosis responsible for huge number of undiagnosed conditions. Clearly not all but possibly the majority and at least the plurality. I think it's the most under diagnosed condition by absolute numbers and work should be focused on correcting that until it is at least the second most under diagnosed condition.