How diagnositc is obsessive interests?

For a few years now, I've thought on and off about the possibility I might have Asperger's Syndrome. The major symptom I have is obsessive interests, I've had these since I was a child. For example as a child I liked birds and sometimes that is all I would talk about, I would even make school projects about birds when they weren't suppose to be. I also have meltdowns (severe as a kid to the point I disturbed the classroom) and some sensory issues.

But I have the ability to read facial expressions and have some social skills (though as a child, they listed on my psych reports I didn't have any). also I look people in the eye when I talk to them.

A couple of my past therapists thought I had it, but other people say I'm too high functioning. I also have some sort of mental illness, they currently say it's bipolar disorder now, which complicates things.

Anyway, my main question is is how diagnostic is the interests? Does this show up in other disorders? Or is it a big red flag?

Asperger's should not be diagnosed by a therapist guessing. It should be diagnosed with proper testing.

My own tests took 2 days...

I think the "obsessive" interests can show up anywhere, especially when you are talking about kids. Autism is on a spectrum and I'm sure in the "mild" area are "tendencies" which bleed into other diagnoses and problems/non-problems. Look at bipolar individuals during mania, for example, they often can stay up, multiple days in a row working on a "project" that has caught them. People with obsessive compulsive disorder can have collections similar to a person with asperger's, interests.

What do you think would change, if you had this diagnosis rather than another?