It's both. Child neurological development goes through a lot of mirroring the environments they observe in play, and mapping them onto stuffed animals, dolls, bugs, pets, toys, etc. There's an age where kids are developing interiority (children do not have an "inner voice" and do not develop it until 5-7, typically) and during that time, a lot of their play is them learning the rules and developing empathy (children do not have a concept of being able to put themselves in others shoes until age 3-7, typically).

Autistic children are often times very interested in learning rules and applying them in other settings. Autistic young women, especially, are navigating a complicated social environment that strongly encourages them to understand the rules of what it means to be a woman in society. Learning those rules and then saying, "Ok little (bugs|stuffed animals|toys), here's how things work" is both a thing kids do and a thing autistic kids do.

Couple that with special interests (dinosaurs, trains, bugs, bones, whatever), and you'll often see autistic kids getting WAY into one particular thing and then mapping the world they experience onto that thing.