Try the test with hip abduction. the results are obvious. The information is the most objective.
The facts will speak for themselves.
Pelvic angles deviate little in those with no back pain.
Pelvic angles deviate greatly in those with back pain.
Your scepticism is similar to Andry Vleeming,whom I have spoken to, but who is pursuing the problematic SI joint. I feel the joint has little to do with it.
How many joints of the body are supposed as stuck as often as the SI joint? That should be a twig to our thinking that maybe something else is the problem.
Try the test and note your findings.
Best regards,
Neuromuscular.