Fg Off Bas, there was still a slot on the 1369 for 'not yet fit'. It was a catchall to avoid the Redress of Grievance charge if you put 'Unfit'.
Many fg off were dischuffed that they had moved up the career ladder and became eligible for SDO and other flt lt duties such as courts marshal. They had much rather been professional aircrew exempt niff-naff and trivia.