Hello, on Patreon you have access to the latests dev builds with the latest content. That is the only benefit of Pledging on Patreon, however you don't get free updates there once you stop your pledge.
My apologies if my confusion is just rooted in a fundamental misunderstanding but doesn't the $19.99 patreon subscription includes a permanent itch key that'll allow you to receive updates 3 versions behind? I guess my main question is that if there's a difference in buying the game for $29.99 directly or receiving a key for $19.99 instead and then canceling the subscription.