result of the first test suggests that there is no strong involvment of any knee flexor (i.e. exclude hamstrings)
result of the second test suggests its either a problem with a knee flexor or a nerve problem which is not located directly at the nerve exit at the vertebral column

One of the gluteal or transversal pelvic muscles (such as piriformis) may be involved and/or may slightly compress nerves which are in between these muscles. Gluteus maximus pars inferior might cause the typical pain in the "hamstring area" then again nerves may cause this as well.



Personally i`d approach the issue with soft tissue techniques such as deep friction on gluteal/pelvic muscle insertions and "tender/trigger" points (or whichever terminology is typical for points which are very painful during palpation).
If i wouldn`t be able to find any tender points during palpation of the gluteal area, I`d have to try a different approach

^This should be done by a professional but pretty much any physiotherapist should be able to work with the terminology deep friction

You can also try applying heat to your gluteal region with a heat pillow or something like that - this increases local blood flow and should reduce most nerve derived pain and improve healing in damaged muscle tissue. However, heat by itself is unlikely to solve your problem.
I`d advise against stretching exercise for the gluteal/pelvic region while the issue is still present especially if they increase pain afterwards/during the stretch
I`d advise to strengthen the muscles which are affected the most after the pain has reduced.

Also try to check your daily life for situations which cause excess stress on the aforementioned muscles and avoid those - excess stress means permanent stretch/permanent (even if weak) contraction. 3*50 squats every three days are not excess stress.



Not much more i can do via online forum. I find the conclusion of your physio reasonable though nothing is ever 100% certain.
Make sure that you dont do anything on your own which increases your typical pain.

Hope you get well soon , cheers