I mostly meant the specialists that make up these theories, what people do they see? I don't know how it works in the UK, do you have choice in the specialist you are able to see?
In theory you do have a choice but in practise it's not quite so simple. The GP (primary care doc) is the gateway to specialist services. The GP will usually decide which speciality you'll see & may want to refer you to a specific doctor, the health authority may refuse to fund you seeing a doctor outside your region if they believe there is a doctor with appropriate skills within your region and so on.
Many patients won't want or feel able to have a confrontation with their GP, may be concerned to be seen as a trouble maker as you can then be dropped by the practice. The way practices are set up some.people may only be covered by one practice so being dropped would exclude them from all but emergency treatment.
If a specialist is prepared to back you in getting the benefits you need so you can eat and keep a roof over your head then you may have to be prepared to accept his diagnosis - even if you don't believe it's true.
The specialist who sees you may already have made up their.minds based on any notes they have access to. I have seen specialists who are utterly convinced that my immune system is the cause of my problems. On the other hand I have had the experience described above.
On top of all some doctors have no interest in your opinion, may listen to you out of politeness and then write something completely different in your notes and letter to your GP.
Patients often just don't feel well enough & don't have the cognitive capacity on the day to argue their case.
A lot of patients don't understand and don't want to be involved in the politics, not realizing the full implications. By the time they do, it may too late & they're saddled with medical records that prejudice the minds of most other doctors before they even walk in the door.
It's a very unequal relationship.