It pulls the package names to revert from the PPAs from the /var/lib/apt/lists/whatever_Packages files that there used to be one of, now there are 2 (one for each arch) and the file names in there don't have the arch appended to the name for the foreign version
It pulls the package names to revert from the PPAs from the /var/lib/ apt/lists/ whatever_ Packages files that there used to be one of, now there are 2 (one for each arch) and the file names in there don't have the arch appended to the name for the foreign version