It's not exactly the only series with different subgenres in the same universe. C&C did it, Warhammer 40k did it and I'm sure people can come up with more examples.
It doesn't exactly take a genius to figure out Dragon Commander isn't a RPG when looking at the official website for 5 minutes. If two different games sharing the same setting is too much to grasp for some people then ... really I don't know anymore...
