It says it in the description: A special thanks goes to our Patreon supporters, whose contributions make it possible to keep adding new characters, maps, and exclusive modes.
Pretty sure you need to make it more clear than that.
Yeah, one can infer about it without even clicking on the download button considering the demo's button is alongside it, but I'd recommend saying it outright at the bottom of the page that only Patrons get the full game and if people like the demo they can pay for that.