Purposeful. I don't exactly remember why at the moment to be honest, but it is only packaged in the upgrade packages; new installs won't have it.

OK, I think my commit messages (and their contents) make sense.

Back on the dev branch, there was this commit which added it followed by this commit for the update server data.

What that's doing is essentially registering the pkg_weblinks extension into Joomla and adding its update site for existing installations (coming from 2.5 thru 3.3). As the weblinks extension is a package extension type, its manifest is needed for the full package to be properly installed. So, we use our scripts to include it only in the update packages to dynamically register the "new" extension and for future updates, if it's in the package but you've uninstalled weblinks, we simply just delete it.

Thanks Michael! Closing this...