No, the Panel Physician does not make the final decision on your admissibility or inadmissibility. The Panel Physician only gathers medical information during the physical examination and add it to your medical records. After you are done with the blood work and the X-Rays, the PP submit your case to your immigration application.
The immigration officers will then decide if you are medically admissible or inadmissible. They can return your medical case and ask for further tests.
Medical inadmissibility rules for excessive demand do not apply to refugees and their dependants, protected persons, or sponsors of the family (dependent children, spouses, common-law partners).
Importantly, if the government determines you are medically inadmissible, you will receive a procedural fairness letter explaining why. However, you will be allowed to respond and give more information before a final decision is made.