What are your thoughts on reservations in post graduate studies (specifically in medicine)

Let's agree that a ST from rural village has extremely difficult journey to pass class 12 and can't compete on similar level as GC who may have far easier access to coaching centres among other things. Any socioeconomic barriers that may be plaguing 12th pass is virtually eliminated once he joins mbbs. Free/heavily subsidized hostel, canteen food, exposure to exact same patients and hospital and they pass out giving exact same exam. Once they become medical officer(UG), they have basically same salary and most likely on similar financial status. What is rationale then for giving reservations in PG level? Do proponents believe that sc/st have inherently lower capability to give PG exam with their fellow colleagues after passing same exam and more or less on same financial level?