I believe it's the only way that Google can make the App Archive feature works within the current architecture: the replace the existing app by a small shim with the same AppId to save space, and that allows the system to retain the local user-data since it's not actually uninstalled.
And when you load the shim, it redownload the app to be used again. The only way to achieve that currently is to "upgrade" or replace the app by a shim with the same digital signature, on the system will block it.
And when you load the shim, it redownload the app to be used again. The only way to achieve that currently is to "upgrade" or replace the app by a shim with the same digital signature, on the system will block it.