It's closer to a macOS bundle than a single script with '#!'. It's at a higher level of abstraction than linking a single script file to an executable.

It would let you build, say, a Ruby interpreter which declares itself as a host, and then package a Ruby application that makes use of the interpreter, including its libraries, native code extensions, and all the related assets.

The Ruby application would behave like a native application, with its own identity in the Start Menu/Task Manager and its own sandbox/entitlements. The Ruby interpreter and the packaged applications would appear separately in the uninstaller list in Settings, and presumably could be distributed via the Microsoft Store walled garden.

The whole 'Windows app model' concept is about bringing something close to the "one icon = one app" experience from mobile to Windows, instead of depending on heuristics or uninstallers to figure out which set of files/processes are part of a single "app" from the user's point of view. This is an extension to that model.