I tend to agree with your approach. The issue is that in order to perform a laminectomy some of the muscles need to be reflected off the thoracic vertebrae in the region and neighbouring spinal region. Your rhomboids are attaching in this area and they therefore won't have a great potential to cling on to their attachments in the beginning. That is why I suggest bouldering first before you have to hang to much off the shoulders. A peg board might just be to much load on that muscle attachment at this time.

Think of it as that relationship of the muscles attaching the scapulae to the spine and you should work so as not to put to much load on them for the first 3 months. That said a gentle contraction along the normal direction of the fibers is a good thing. Only the surgeon knows how much work he did in there so only he/she can really say how long they want you to be super careful. My opinion is that your best rehab is in the climbing wall but with advice from the local sports physio who can guide you in acceptable exercises to maintain and retrain the rotation elements of the spine in that area. We don't want tough scar tissue inhibiting movement that might tear on the first 'dangle' by the finger tips

So I think if you have a premise for deciding what is an OK exercise and what is not then you will be able to work forward on that basis. Discuss that with the surgeon in light of what is and is not stable at this time and what will become stable and what will be lacking in the future.