[chuzz]

That does not sound reasonable, why would the shim ever need to be signed with the same key? why can't a system supporting App Archive make an exception for the shim? if it can't for hardware reason, why can't they ask key owner to sign the shim app? That would degrade security but is not as bad as requiring to give away the private key.

[Karliss]

If they implemented this properly there wouldn't be any need for shim. So talk about ignoring signing requirements is meaningless. Adding single flag in the installed application table not to erase the application settings+icon cache would have been enough.

Using a shim application is a giant hack, allowing to implement this feature by updating only the Google Playstore without modifying the base OS and how it handles application installation and managing process. This is only relevant only because most android phone manufacturers are bad at providing Android updates. Some Google engineer probably felt very clever, that he came up a with a trick which in theory allows adding this feature to older phones that probably won't receive any Android system updates.

Google could have also allowed application developer to sign the shim. That way getting the benefits of archiving feature on older phones, without forcing app developer to give up the key.