I said this before. I've been reading a lot about BPD and from what I read, many patients with borderline disorders have been misdiagnosed with many mental illness and disorders before getting the right diagnoses.
Some psychologists point out that one of the reason is bc of the nature of the disorder itself. You know, unstability. The symtoms also present themselves with a great unstability, so the patient may give an impression very different to the one, (s)he gives another day according to the mood swings.

Many patients who end up in a hospital for a suicidial attempt or because of eating disorders are diagnosed with depression or anorexia.

From what I have read, even when this disorder is pretty wellknown now and there have been lots of advances, it's a relatively new disorder. So, it's not strange that proffessionals make errors in the diagnosis.

I think it's easier to diagnose extreme cases but this disorder are in individuals in very different grades. A person with bpd is not the same to another with the same disorder.

Then, there are hidden symptoms that are hard to know by the psychiatrists when even the patient unknowns them and see them as normal.

Very few it has been done to know about AvPD but in my opinion, the view that has been offered about BPD has been very harmfull for the patients. So, It's not strage that professionals are very reluctant to give this diagnosis and in the same way, patients don't feel comfortable with the dianosis.

My therapist denied me that I had this disorder and my psychiatrist asked me to work on the issues I have and don't worry about diagnosing me.
I went there with the DSM's symtoms and I explained to him where I see myself reflected and he even got angry with me. He said that personality disorders are not found in the most cases, in a pure way.
So, I think I have a personality disorder mixed with trait from here and there.
It doesn't mind. I don't like labells.
I was very released when I was diagnosed with AvPD eight years ago bc since I was a child I didn't see myself like a normal person and it was a released to see that other people have something similar than me.