I think it was just thoughtless. He decided to belay off his harness, and instead of taking the ATC Guide out of the system, he just grabbed the biner attached to it and ran the rope through it.
The guys who posted the photo realize it was a lapse-- I'm starting to feel bad now about posting it, so please don't be too hard on them. Here's the page it came from, and the people who did it posted comments about their mistake:
link