The import feature will completely overwrite the app object including styles, elements, workflows, data types, etc. Technically, the app data itself will remain unaffected by the import so if you are taking incremental snapshots that don’t affect the structure of your data types you won’t be destroying stored data with each import. The User data type for instance which is present in all apps will still have what ever user objects you’ve previously created for that app regardless of what you app import.
I think you’re on the right track with your second statement. The key benefits that we envisioned was the ability to take snapshots of your application and manage those backup files outside of the bubble editor in whatever way you see fit.
We want to make sure that we are empowering our users to manage their applications how they want. I wouldn’t be surprised if we go back and flesh out this feature a bit more once we see how / if the community starts using it. I can’t really say for sure though. For now I encourage you to play around with the feature, get a feel for what you can do with it, and feel free give us any feedback you can! 