I think the OP points to several larger issues involving concussion and concussion-like symptoms.
The key to this question is actually in your state rule 6A,
An athlete determined to have a concussion or have concussion-like symptoms will be removed from practice or competition and is not allowed to return to practice or competition that same day.
Did you determine the player had "concussion-like symptoms." If so, they may not return that day. End of discussion. No written approval from doctors, etc. can overcome this first standard.
If you did not make that determination (based on everything earlier in the state policy and other concussion training you may have), did the training staff? If so, the same rule applies. There is no exception.
My state has the same requirements: if a player exhibits signs of a concussion, they may not return to play or practice that day. No exceptions.
As officials, we are required in Massachusetts to take a course on concussion recognition annually. We have independent judgment and authority to determine whether a player has concussion-like symptoms. If we make that decision, the player cannot return to play that day, no matter what.
I would much prefer to defer to the judgment of athletic trainers and health professionals, since my knowledge is limited to the on-line courses and related material I read.