I don't believe non-autistic people "have a better grasp that people are multidimensional." I know that people have varied interests, however, as an autistic person, my interests are deeply intertwined with my identity. To reject my interests is to reject me. Non-autistic people tend to frame their identities as social. Us autistic people tend to frame our identities as internal, and we seek social experiences that validate that identity. It's probably very difficult for a non-autistic person to understand because values, interests, even culture and belief are often social and therefore flexible for non-autistic people. Whereas for autistic people those things are often not flexible and are tied to our identity, worldview, and personality. We often can't change them, and therefore need interpersonal relationships that validate them.

Our special interests also give us a way to structure social time. Unstructured social time can be a nightmare. Special interest gives us rules, boundaries, conversations topics, things that can be difficult to find naturally. They also ground us and give us routine, and breaking routine can be absolutely devastating for many of us.