I still maintain that one reason the guy as able to do that is because he didn't act sneaky or surreptitiously.

When somebody carries a huge cutter and strolls up to a bike and cuts the chain, I'm going to be thinking, "That MUST be his bike, because surely no thief would be that brazen."

I would love to see them do the experiment and have the thief look like they're trying not to be notice or caught.