It will vary by Patreon creator, and Patreon is constantly making changes which impact how any of us may run our own Patreon. Their data shows that introducing a "free" category can be a way for folks to follow the creator and this can mean many things: see that they post often/consistently, get a sense of what they post, or simply enjoy free content. The platform encourages creators to use this feature and has strong statistics showing it helps us.
Some creators do a lot of free posting. I follow a few. Others do very little. In our case, my hope is that it shows how consistent we are in posting our show notes, which is one of the main benefits, along with access to our Discord. We really intend for the Patreon to be a place where people go to support the show. We are already making the show, but it is entirely likely that without any support we would have closed up shop a long time ago. It takes a lot of work to make the show. Funds help cover equipment, software, and most of our time. It also means a lot to us, especially as supporters then hang out with us on our Discord, forming a community we enjoy being part of. If the "free" tier can at all bring someone into that, I'm all for it!
Edit: for Mastering Dungeons, an example free post is
episode 256, which we made free so that anyone could get access to the links in that show. It's an example of our show notes.