No idea. I have seen other projects that distribute fdroid and Google Play variants in their git repos, along with the straight package. I guess if you've already got the Google play or fdroid variant installed but want to start pulling from the repo, it provides an easy way to continue on without having to uninstall the old variant. Because sometimes if you have one variant installed and try updating to a different variant it fails, requiring uninstalling the old variant and then installing the new variant fresh.