This is a "fuck around and find out" scenario. The developer you mention in your OP is most likely in that situation - under the radar, but if one disgruntled fan/former subscriber gets pissed off and reports the developer. Boom goes the dynamite. (Unless it is the developer I am thinking of, and then what you need to know is that they already ran up against Patreon in the past and there is an agreement between the two entities about certain things).
Honestly, if you want to create a game that would violate Patreon Community Guidelines and TOS --- then don't use Patreon. The end.
You could get caught day one.
You could get caught month one.
You could get caught year one.
You could get caught year ten.
You could end up never getting caught.
However, is it really worth it to take the risk for, on average $100 USD per month? The vast majority of adult game creators on Patreon bring $100 USD or less per month even after 3-4 years on the platform.
If you're already going to make low bank, use a platform that is more friendly to your content (if you can find one - I mean almost every platform has similar rules as Patreon... they just currently don't enforce them as stringently, but as they get bigger, watch out).