Yes i think that makes a lot of sense. It might also explain why the initial caller thought the man was acting in a strange fashion.
Perhaps if the police had recognised the situation they could have allowed the man to his feet and tried to speak in a calming and re-assuring manner and perhaps tried to get family members on the scene as quickly as possible.
Police have a certain culture which i assume is there to protect themselves and i can sympathise that they are not knowing ahead of time if they need protection or not. It is a culture that is foreign to most of us and probably a lot more foreign (and dangerous) to a person with autism.
I also think that there must be a better way to restrain people other than pinning them to the ground and waiting for chemicals to be injected. For many people, for various reasons this process seems to put a lot of physical and/or mental stress on them.