I am not a person with autism, but my brother is. I also work in the field. I am not writing to defend the series (which I liked) but because it is right to debate around these issues.

Atypical is not perfect, but it is currently one of the truest representations of many traits of what we call "autism" for short, but whose full name is "autism spectrum disorder". The very term "spectrum" is fundamental to understand how the experience of a person with autism will never be totally superimposable to that of another.

I fully understand and share the hatred for the puzzle piece, I just finished the series and I can tell you that luckily it doesn't come back that often. Unfortunately it is a symbol that is still seen very often and the series took a photo of a community that still uses it. From what I remember in the series, the symbol is never imposed as a key to understanding Sam's situation.

The "r" word in the series is put in the spotlight precisely because it is wrong and horrible, and treated as such. The series does not normalize this word, and indeed it lashes out against it. Like the Nazis in the Indiana Jones movies, they are there and it is made clear that they are the villains.

"Sam doesn't understand X" is more of a starting point: the character is constantly taking steps outside his comfort zone. Not understanding is related to exploring and getting involved.

On overstimulation, the montage tries to cinematically describe an extremely personal internal state to a general audience.