I had same pain before my fusion and now 2 years after my first fusion same pain in same area; and he is right about more pain after you get up after sitting position. I have to move slowly to get up from a chair.
He is too young, but nobody knows if he ever injured himself in that area. You don't need a lot to do so. My injury in that area was 30 years ago when I fell on ice and this pain was with me for all these years.
The only thing is: no tests showed anything wrong with me; only when I had lurabar fusion DR descovered another problem and was very suprised.
Best of luck to you.