Who has authority to override Army Profile Code B (Block 2) assignment restriction?

A soldier I know is returning to active duty after a less than a year stay with the WTB and received a permanent profile with a code B in block 2 (Soldier has minor impairments that may disqualify for certain MOS training or assignment). In the comments the military doctor identified the Soldiers requirement to be near a specific type of doctor, in this case an Orthopedic Oncologist due to the 5 year battle this Soldier had with a very specific type of benign bone tumor (Giant Cell Tumor). This Soldier has received assignment instructions for Fort Polk which they are actually ok with. However, they are concerned as the closest orthopedic oncologist is in Houston or New Orleans 3+ hours away. The Soldier is required to have follow up appointments every 3 months with an Orthopedic Oncologist. When the Soldier talked with the Special Actions Branch at Fort Knox, they were told that because they are in "recovery and monitoring" that an oncologist would suffice. While the Soldier attempted to talk to branch, branch told them needs of the Army and medical requirements made Fort Polk their only option and was obviously not very helpful in determining if another location was available. The Soldier is trying to find the answer of who has the authority to say that an oncologist will suffice over an actual orthopedic oncologist. The Soldier is concerned because their first doctor was also not an orthopedic oncologist and did not understand the tumor and actual caused it to spread to their soft tissue and eventually led to them having a reoccurrence while deployed, additionally missing that the giant cell tumor had spread to their lung. This Soldier is concerned due to having a rare type of bone tumor most doctors like the Soldiers first doctor want to have treating a patient with a giant cell tumor on their resume, as sad as that is to say. I'm trying to help the Soldier but cannot seem to find the answer either or if an answer actually exists. Is it merely a recommendation that the Soldier be stationed near an Orthopedic Oncologist, or does a oncologist truly suffice or is 3+ hours one way due to the frequency of visits sufficient to meet the requirement of "being" near an orthopedic oncologist. It seems off to me that a Soldier returning to duty from the WTB with a requirement to be near an Orthopedic Oncologist like Walter Reed (like it was recommended in the profile) would not be that difficult.