Ah, I see the confusion. That "exclusive content" thing is boilerplate for the itch.io feature I'm using to allow for free community copies. If I could turn it off, I would. There isn't anything extra. But that's the only way I can set up community copies for those who can't afford the game otherwise.
Actually, if you paid more, I'd add even more community copies to the bin, so there would be more for other people due to your generosity. So there's that.