I thought it was. So this article by an Ehlers Danlos patient was enlightening. As the author says: it's a murky area.
I've said it before, and I'll say it again, flexibility (muscles) and hypermobility (joints) are not one in the same. Another major misconception in Ehlers-Danlos Syndrome (EDS) is in regard to stretchy skin. In 31% of cases, highly stretchable skin is not present. EDS actually results in a loss of tissue elasticity. Too many doctors are unaware of these facts, and the misconceptions are hurting patients.
As hypermobility goes up, flexibility can often go down. As is the case for me, muscles can tighten while attempting to stabilize hypermobile joints. Many with EDS, including myself, have extremelytight hamstrings, even in childhood, as the hamstrings try to protect the hypermobile spine and joints. Can EDS patients be extremely flexible? Absolutely. But, flexibility is not what doctors should be assessing when EDS is up for diagnostic consideration.