Think like this:
What stops anyone from just buying the game, downloading it and keeping it after returning or when you give it out via Patreon they can claim it also, I think it's really hard to make a system that functions well for people like you who have doubts, people who simply exploit such things and people that really just want to be patreons.
Many people see patreon as a one time purchase thing because you can just do that, for like a month or whatever and keep what you got.
tldr; not easy to revoke access to something you have already on your disk, and if you don't include some sort of drm there's nothing stopping anyone from sharing it with friends or post it somewhere.
Some people can be jerks, but there's some nice people on this world too :)