are they donating to play the game or donating to support the creator?
I thought Patreon was a place to support creators???
It's 50/50.
The way Patreon is setup is so that, in a broad sense, the more you donate each month, the more you are rewarded. Most creators have donation tiers (for this game it's bronze, silver, gold, etc.) which have certain rewards for each tier. Some creators give voting power for new things to be added to their game, Patreon exclusive posts, early access to game updates, sneak peaks at new content... the list goes on.
Then there are creators who also provide in-game bonuses to certain tiers for their Patrons. Almost like a "pay-to-win" feature. The developer of this game is one of those creators. This is meant to give the people who donate more of a reward/incentive to keep donating. Although there is a lot of debate on whether this is too much or not (as there are many popular devs who don't do in-game bonuses and are still extremely successful). It really just depends. A lot of people are willing to pay for those bonus features regardless of how some people view it.
Personally, I think if a game is good enough you don't really need to provide in-game bonuses, as there are MANY other great ways to reward Patrons without tampering with the gameplay itself. Plus, if you think of it like a monthly subscription, is a game like this really worth supporting for just a smidge of bonus content? Not really... The thing is that people will support you if they enjoy the game no matter what, so there isn't really a reason to add in-game bonuses that will make a lot of people upset other than simply trying to get more people to pay money to Patreon (as there will absolutely be people who ONLY pay on Patreon specifically for that small in-game bonus).
(mainly talking to the devs in this next part)
Think like a consumer for a second.... "This game is fun, but I have to pay for certain features in-game, which sucks..." Compared to, "This game is fun, and it has all this content for free?!!!? And I get bonuses if I help support them, like voting and sneak peeks??? sign me up!"
The difference here is that even if you ALSO give Patreon bonuses (voting, early release, sneak peaks, etc.) IN ADDITION to in-game Patreon exclusive content, you already have created a bad impression on someone just finding your game by telling them they need to pay for a portion of the content. You might as well sell it on itch.io if you want to do that.
Is it a little grimy? Yeah, kinda.
Does it rack up money? Yeah it definitely does. But if you're okay with the game being built like that, then by all means go for it. Just don't be upset when people scold you for it, as many people will dislike it and can lead to creating a bad reputation for the game.