Yeah but it's not a migration. E.g. you don't get access to your data in many (most?) cases, often thanks to security consultants like myself who see their scanning tool warn that backups are enabled for an app and put a recommendation in the report to not let users access their own data. (FTR I've never done that, but had colleagues that I had to argue with...)

Just yesterday in an OpenStreetMap chat, I had to disappoint a user who wanted to access a locally stored recording in some app. They didn't have root and so they couldn't access it from outside the app.

Backups aka accessing your own data is one of the biggest problems I have as an android user, with as only solution rooting the device and treating it like a normal desktop OS where you also have root, except various apps start to complain when you do so. Apple really has the nicer solution here via the iTunes software.

You're absolutely right about the data, but I think the context of this thread was more about transferring the .apk itself, to avoid having to download (and potentially purchase) it again.