The difference between the child stacking thinga and Minecraft is that the child stacks objects out of a mental desire. He does not do it with purpose, but simply because he likes to see things stacked up.

In Minecraft you stack cubes with a purpose to build a structure. It would be more similar to this child's autism if they had stacked anything on top of one another witgout discretion for different material types, but Minecraft users have a purpose and goal in mind.

Is there something wrong with that?