Non-sensical benefits

My husband is on Keycare Plus. Approved network GP requests thyroid function test. Discovery won't pay for it. As per call centre, GP must refer patient to a Specialist who can then request the test THEN Discovery will pay. So they will pay for a GP consult AND a specialist consult and then only for the test. Are GPs not qualified to read/understand a basic thyroid function test??? Is this not a complete waste of money? Please give me a MEDICAL REASON why, not just that that is what you pay for.