Remember this happening at the time since I also bought this while the game was still $6. Still wondering exactly why it works like this but I'm glad I scrolled down the comments again to see you address this (probably would have been more convenient for everybody if this comment was a development log post instead. That way it'll be one of the first things people see on this page and clear up some confusion).
That being said, making an attempt to poke into the situation again. As much as I did enjoy this game (especially for an RPG Maker one these days) I'd rather not go through a whole new full purchase just for an update, let alone for something that's the equivalent of a game still in Early Access. Only asking since there hasn't been much communication here.