This is being debated in the thread opened to discuss this issue. At first, I understood it to be related to webcam content and other real porn activities that I saw take place on or through some patreon accounts.
Strictly speaking, "using Patreon to raise funds in order to produce pornographic material" is the very definition of what game developers are doing there, despite the legal loops that, as you say, can be employed to argue a case. But, curiously enough, games are not explicitly mentioned in the text, and some of the creator pages that were taken down seem to be up again. I have even read some are saying they are handling things with Patreon and will be back with some changes (problematic content hidden under patreon-only posts, etc.). Therefore, if the policy affected the activity in its totality, this should not be possible and all the developers should have to change their projects radically, or remove them from Patreon.
Let's see if they clarify things in the next days, but, as of now, I doubt they change is so radical.