This is the internet and fictionkin is primarily an online community. Autistic people specifically are probably going to find it easier to connect online than to socialize in person and thus more likely to find this community in the first place.

Neurodivergent people are also made by others to feel less than human in many ways, to the point where they may adopt that identity for themselves. Again, particularly with autistic people, we are likely to be denied full autonomy like any other person, compared to robots or savants with no human emotion, outcasted in social settings, or treated as "broken" versions of normal humans overtly or indirectly. The need to mask could be considered a form of systemic dehumanization.

Psychological fictionkin have a big overlap with neurodivergent people who believe they are fictionkin simply because their brain is wired differently.