An added note:
It looks like CCP may be smart enough to recognize an Acrobat Pro standalone license key. (I accidentally entered our XI key instead of the DC key and it let me build a package for that).
It also looks like we may have been issued a couple of invalid license keys for DC--they don't even serialize directly downloaded installers. If that's the case, this may be working the way its supposed to. The document linked in my previous post still implies that Adobe wants us to use setup.exe rather than msiexec.exe, but then it says, "6. Proceed to deploy the Creative Cloud Packager created MSI or PKG file to the client."