My theory: there's a version number that devs set on an app, and there's another version (say an integer starting from zero) that Apple puts on apps. They bumped their version, leaving app's version intact.
I'd say that's a good theory, and if they baked it in from the beginning, it's a great solution to this sort of problem.
The fact that Apple is so strict about monotonically increasing dotted numbers for version strings led many of us to believe that they were being parsed for important things inside the App Store publishing platform.
But maybe they are just part of the UI. Apple is known to have strong opinions and strict adherence requirements about that, too.
Do they need to update any part of the app on the devices for this? I think it could be something as simple as "if a device checks for updates, check whether it (might have) gotten a faulty binary. If so, lie to him that there is a new version, and send them a version he already has, but use a correctly signed binary this time".
