The "View a Packages Contents" deals with the new package\bundles of Mac OS X. In Mac OS X Applications and other rich objects are actually directories. The higher levels of the operating system show these as single objects. If you have Mac OS 9.0.4 and Mac OS X on the same machine and you look at the Applications directory in your Mac OS X area in 9.0.4, you'll see a bunch of folders (like "AddressBook.app"). In Mac OS X, you see the regular AddressBook application. All of the resources (from the executable to items that would have traditionally been in the resource fork) are inside the AddressBook.app directory, which should appear as a single object. This is how things have worked on the NeXT since the beginning.
In Mac OS 9.1, AddressBook.app *will* appear as a single object and not as a folder. Using "View package contents" (a feature also in Mac OS X) opens the package up like a Folder. It's only there on certain objects, most of which are likely to reside in your Mac OS X space if you have the public beta. As more Carbon apps are built to run in both environments, getting Mac OS 9 to treat these the same way as Mac OS X does is important.