Archers are usually sold in freshwater and they appear to do ok in freshwater, though better in brackish. So, I see no problem with the screensaver including them.
Fiddler crabs also are fine in freshwater for a few weeks. What's your main complaint? That fish that can live in freshwater for a while are in a simulated freshwater fish tank? Would you prefer they make you pay $15 to put the crab in then simulate it dying a few months later because it's not quite ideal?
Oh, you also forgot to complain that the screensaver lets you put something like 50 tiger barbs in a 19" tank(On my screen, maybe larger or smaller depending on your screen size.)