That doesn't really make sense unless they have a way to flag higher-risk charges and route them to a processor that is more risk-tolerant (and usually more expensive). Eg. I could see segmenting the charges for the first month or two into a higher risk bin, and then moving recurring customers into low-risk bins on processors with cheaper rates.

But a rates a rate?

There is a difference between straight up porn and fan-service (OnlyFans) and the adult artwork and erotic educational content on Gumroad. I would be surprised if these suffer from the same amount of chargebacks.