I knew that I had a bit of trouble reading people, but I didn't think I had trouble with their facial expressions :/
I thought the kid/guy looked amused like "oh, cool, we share the same interests" type of look.
I asked my mum about this, and she's usually very good at reading people, and she got it wrong too, she thought the same as I did, that he was amused. Maybe that means the video is wrong, and not us? Or maybe she's just on the spectrum too, she does have some traits.