According to them, the page was put under review because of a couple of image render packs from some tier rewards (What exactly the issue was with them was not mentioned) and that a third party site had links to download the game.
Let's assume for a minute that the guy isn't lying like he usually does. If that's true, the guy is more lucky than good that Patreon obviously doesn't bother to play his game or that no hater has bothered to send in screenshots from the game yet. Not to mention the references to the obvious copyright infringements against Universal Music. In life, the guy doesn't have the license to use "Chariots Of Fire" in his game.
But let's be honest. He's lying like shit again. Patreon doesn't care if you offer your own content on a third party platform. Even if it's free. Many creators does that, like podcasters, artists, musicians, streamer, etc. They only care about what you offer on their platform. For example, if you offer special benefits on a Discord based on your Patreon tier, Patreon is therefore directly involved. That's why they interfere if there is content on some servers that Patreon does not tolerate.
What they also don't tolerate, of course, is if you collect money on Patreon and engage in illegal activities outside of Patreon, e.g. as a terrorist you will have a hard time financing your propaganda podcast via Patreon. But they're not stupid on Patreon. They know very well that content creators have no influence on third-party platforms. But they can also recognize whether a creator independently publishes things that Patreon doesn't approve of. An example would be an incest patch created by the dev, which he offers here on F95, or if patches suddenly appear that simply set a variable in the game, which would show that the violation of Patreon's TOS was initiated by the dev himself from the beginning.