Meanwhile, you have a large group of people with lived experience sharing that experience. Surely that counts for something?
Not necessarily.
My kid has been diagnosed with autism and ADHD, and going through the diagnosis process, we realised that I fit a lot of the symptoms. Speaking to friends with various disorders and mental health issues, as well as reading up on them online, we found out that autism and ADHD have overlaps in behaviour. They also overlap with anxiety, OCD, bipolar disorder, and a few others.
The bouncing knee seems to be recognised as a stim for autism, hyperactivity for ADHD, and a nervous behaviour for anxiety. A group of people could convince someone that it’s a sign of whichever diagnosis they personally have, while not knowing about the others, all while not realising that the person asking is just suffering from caffeine withdrawal.
Obviously this is an oversimplification, but hopefully it helps to point out that all groups have their own blind spots, and we all tend to colour things with our own perspective.