This is normal for many of the early non-parallelogram derailleurs. The spring pushes the cage to the left (big cogs), the cable pulls it back. On the disraeli gears site this is called "normal low logic" or something like that. Simplex Tour de France, and many other huret and Cyclo mechs worked this way.

This type of derailleur has two main problems. First, it is difficult to remove the rear wheel and difficult to put it back. Second, if the bike falls over on the right side, the derailleur cannot deflect the way a parallelogram can, so it ends up supporting the weight of the bike. It usually gets bent in the process, often without the rider realizing this has happened. If this is the case, the rider is at a great risk of shifting the derailleur into the spokes, much to its detriment.

Face it: bikes do fall over now and then. This is, I believe, the main reason this type of derailleur is rarely seen nowadays.