FFXV Kinkmeme

Not OP, but being someone who finds the "autism headcanon cliche" way overdone to the point of being a little offensive at this point, it's probably because there are points in the game where Noctis doesn't talk very much or seems withdrawn, and sometimes Prompto will comment that he's not showing emotion when he catches a normal-sized common fish but is super excited about fish whenever it comes up, that kind of thing. It's so easy for that headcanon to just reduce any simple personality quirk or enjoyment of anything to just "autism, yup, because being kind of insensitive sometimes is exactly the same as being unable to understand some forms of social cues, and having a favorite hobby that you're really very good at but don't get to enjoy very often because it's an outdoorsy sporting activity and you live in a major metropolitan area is exactly the same as an obsessive special interest that supplements other emotional and social interactions that a person with autism may find more difficult".

Basically what I'm saying is, Noctis has more character tidbits that can be creatively interpreted as signs of autism than most, and it doesn't take much to begin with.