I certainly don't know if this helps answer any of your personal questions but from my research, yes, the outer pelvis bones are made of three separate bones until fusing occurs. Somewhere in the late twenties to mid thirties. Estrogen in early puberty should cause the lower bones, the ones you feel when you sit, the ischium to angle outward. This makes the pelvic outlet large enough for childbirth. Along with that the pubic bones lengthen at the pubic syphasis joint. Normally the upper crest the ilium bones also flare outward.
I had the opposite situation. As a child around 7-8th grade my pelvic crest widened. For a while I kept hitting door frames with my pelvis when going through. My ischium bones are verticle, not as far outward as a cis woman would normally get. Same for my pubic bones. They only slightly lengthened. I'm still searching for a medical person who can answer questions for me. But most any tests would be non covered as far as insurance goes.
