Guessing from the article, but I think rather than attempting to install everything on top of everything else, and then deriving the uninstallation or replacement of packages from conflicts arising out of that process piecemeal, as per the usual package management strategy, with all the unpredictable complexity entailed, there is instead a planned tree structure for the dependencies, so that the switch is analogous to git rebase to a different branch of a repository and not to series of increasingly desperate manual invocations of /usr/bin/patch