Technically, an application bundle can be located anywhere on a Mac; there is no installation process, they’re self-contained and always have been.
The question of how a regular user could be allowed to install something for all users in this fashion, placing the app bundle in the /Applications folder, is no different than when using an installer: ask for an administrator password.
The question of how a regular user could be allowed to install something for all users in this fashion, placing the app bundle in the /Applications folder, is no different than when using an installer: ask for an administrator password.