This is a common practice for such pre-releases. Though they could have added the APK on the Google Play store but then they will have to introduce a new intern

This is a common practice for such pre-releases. Though they could have added the APK on the Google Play store but then they will have to introduce a new internal API where they keep a check on the pre-release users. Can be done but I think this manual distribution can be used for many other things! But it's annoying that they do not want to support rooted devices!