Just for fun I used to check the original DVD's I've as well as the ISO files I downloaded from MS and looked at the file dates: ALL the exact same data, nor difference for the install.wim! The screenshot which you posted with that picture are not from the same installation as of Rob Jansen! Even he didn't show the same screen, his installation was done on an 1GB Ram System while the screenshot from you is done from an installation with 2GB Ram. that said, I see something a bit suspicious with that different file date!
I doubt if it can be called as a loophole. If Windows is downloaded through Upgrade Assistant, then it is installed from ESD via setup. The same setup is used for retail media to install from WIM. Also if memory serves me right, then DISM in Preview can service ESD images too.
Partially Core Single Language is meant for emerging market (similar as Home Basic) & you can't install LP after installing. Besides that it is same as Core. Oh well... you can only get CSL through your OEM.
Think "Windows 8 Starter". It was created to help curb piracy in china etc.etc. and for "a small number of emerging markets".