I'm not exactly sure where this idea came from. It's certainly akin to Betty Edwards' upside-down duplications from her book Drawing on the Right Side of the Brain , but I think my former art teacher and mentor Bob Pennebaker came up with them (maybe not, but he's a genius and he could have!) Drawing on the Right Side of the Brain suggests taking existing pictures or drawings, flipping them over, and then copying them. The idea is to confuse your "symbol system"*, rendering it useless and forcing you to draw what you see. These duplications, however, are not based on actual drawings of something; they are based on nonsense scribbles - take that symbol system!
*Your symbol system is the set of preconceived ideas you have about how thing look. Ask most people to draw a hand and you'll get a circle with 5 twiggy things sticking out, sort of splayed-like. That's what a hand "looks" like. But think of the myriad ways can you position your hand! Sometimes it's hard to accept what you see and draw it because the logical (left**) side brain is telling you, "No, that is not what a hand is supposed to look like!" By drawing something nonsensical, your symbol system has nothing to go on.
**I'm no neuroscientist, and I'm not here to argue whether or not left-right lateralization of the brain really holds water. I do think it's a delightful heuristic though, don't you?