How did his user account lose permissions to a folder of pictures?

He didn’t “discover owner” by opening any permission settings. He is simply asserting that he is the owner of the pictures he took, in a non-technical sense.

The fact that Andrew might have to run this at all means Windows (or possibly the manufacturer of his camera) has fucked up. He should not need to learn about this to use his files. Obviously he shouldn’t have permissions to system files but that’s clearly not what he actually wants.