Commenter Ellen Brady writes:

I actually agree with this theory of the autistic brain not able to prune itself. .My son is autistic and can learn spatial material in a short amount of time but is not able to stretch his thinking overtime and cannot identify social cues or life skills in the long run.

The question is what comes first? The autism or the failure to prune. It could be that typical kids are so interested in people that certain spatial synapses are not much used. The brain identifies a synapse that has not been used in a certain amount of time and prunes it as redundant so that more resources can be used to strengthen the synapses that are being used (the social ones). By contrast if the autistic child has little interest in people and spends all day visualizing objects, thus using the very synapses that are normally pruned and derailing the pruning process.

On the other hand it could be that the pruning fails to occur regardless of what the child does, and the obsession with weird topics is a product, not a cause of abnormal pruning. For example because of a failure to prune useless synapses, the child might have a savant like ability to play any piece of music after a single hearing or know the day of the week of every date in history.