The score has certainly been around. But the book isn't just revised- it's brand spanking new. That complictes things.
Little Shop and others were known commodities prior to their Broadway "debuts". That's the difference.
But this is half-known commodity, half-new. It's almost akin to something like Nice Work if You Can Get It. Sure, the score has been used to tell the same general story. But now there are additional songs, not to mention a new script. The show is NOT what people would know R&H's Cinderella is based on its prior incarnations.
"...everyone finally shut up, and the audience could enjoy the beginning of the Anatevka Pogram in peace."