Yes, it's true that most striped corns have no "clutter" on the dorsum between the stripes, but the more we're breeding them, the more we're starting to see some that are a little dirty between stripes. Some have markings between stripes while some just have echoes of markings between stripes.
The best way to distinguish between them is the width and location of the stripes. On the striped motley, you can see that the colors that represent the markings take up most of the body and are closer together dorsally. On most striped corns, the stripes are not only narrower, but usually cleaner (relatively consistant width) and farther apart dorsally. As you point out, most striped motlies have stripes that are narrow/wide/narrow/wide, etcetera. The ground zone between the stripes is almost always wider on striped corns than it is on striped motlies. There are exceptions in both directions, but I estimate that this rule-of-thumb is about 99% representative at this time.
South Mountain Reptiles