I can't say this is a horrible idea, although sometimes this can be subjective... especially for the writers who are, shall we say, less competent at dealing with branching stories. One of the key reasons why so many stories fail here is because the writer doesn't have a clue what kind of structure they want to achieve. More than a few seem to think they're branching like crazy, but really aren't. By contrast, all of the more successful stories on CYS were written by people who are probably diagramming their stories in some way, and are therefore very conscious of structure.
For a website devoted to branching stories, I think this could be a very interesting feature. As writers, some of us might see that we've written a lot using a certain structure, and feel more challenged to try another structure in the future. All those noobs might pay more attention to the branching structure too as they're reading stories, and perhaps take note how one style works differently than another. And since I believe the difficulty rating is going away, there will be space opening up.
But on the other hand, I also agree that many of the less enlightened noobs will be completely confused by what any of those styles mean. I foresee many linear zombie stories tagged as "Cave of Time". So maybe the solution is to make this an optional rating, with the warning that if don't have a clue what any of this means, it's not for you.