the article you linked to literally says that's not the case. the way it works is that you upload your epubs to amazon and then they convert them from epub to azw3 for you and then allows you to download them to your device. not only is this a rube goldberg machine that doesn't support epub, it's been unofficially possible for years already by changing the extension from epub to png to trick it into thinking it isn't an epub when it is.