Open a bug with Apple about this. They fixed an issue I reported a few years back about being able to launch applications in the Trash. They will likely want to add the same restriction to Time Machine Backups as well.
The bug is in the "find an application and launch it" code, which is distinct from the "user located this application within Time Machine and tried to open it" code. Apple will either make the distinction so that you can manually open an application from a Time Machine backup, or simply prohibit launching applications in both scenarios and require you to restore it to your user partition to do so.
