Read it for yourself!
But what you say is based partly on truth and partly on a mis-understanding. These documents are expressly about Primary hypothyroidism. So anyone who breathes words like "secondary hypothyroidism" or "tertiary hypothyroidism" or "central hypothyroidism" or "pituitary", or accepts they could be in the equation, needs to look elsewhere. If they then go on to spout from these documents, they do not understand what they are talking about.
Patients with normal thyroid function tests
(a) We recommend that those patients whose thyroid blood tests are within the reference ranges but who have continuing symptoms, whether on levothyroxine or not, should be further investigated for the non-thyroid cause of the symptoms.
(b) A further opinion or help with these patients may be sought from appropriate specialists on specialist registers of the Royal College of Physicians or the Royal College of Paediatrics and Child Health.
This makes an absolute assumption that thyroid blood tests within range CANNOT occur in someone with a thyroid disorder that needs to be treated. I do not believe that is backed up by rigorous scientific evidence.