Chill out man. I do exactly what you said, I dl these public versions from Itch.io or patreon, and if the game is interesting, then I buy it when it's completed.
I do have to somewhat agree with the other poster, it seems a bit... excessive... that the free version is 3 versions /half a year behind, when most free versions (that aren't just outright demos) are a few weeks/1 version behind.
That said, As long as it more or less stays a consistent length behind free folks are getting content at the same rate, just delayed, so, meh. Best case I'll just have a massive catchup jump when it finally finishes up, assuming the author puts up a "paid" version right when they finish. (I'm somewhat a fan of the "patreon version to people who have actually paid at least $x model". I consider the patreon "subscription" model somewhat sketch, as you're literally paying the person to draw the games development out as long as possible.)
edit: And of course those devs who ONLY ever make the final game available via patreon can rot. Clearly hoping people forget they are subbing and just keep paying for nothing.