Where did you read that? I doubt it is true. Banks don't worry this much about refunds. Not at the size of Onlyfans. This would have more to do with documentation and potential legal issues.
Stories on the BBC about underage models making money on Onlyfans is what Mastercard and VIsa hate. Especially so soon after the pornhub shit show.
The reason Amex doesn't support any porn transactions is because the chargeback rates are super high for the whole industry. Then take a site like OF that is designed to be as opaque as possible + enables scammers, and I bet the chargebacks are ridiculous (and rightfully so).
OF is a sleazy, corrupt company that gives zero shits about the user experience. They have only ever cared about maximizing transaction volume--that's why they've never even bothered to add a simple review system. They love it when horny people make bad decisions and get ripped off, because it means more money for them. Getting axed by the credit card companies is the product of its own greed.
Hopefully they get replaced by a decent platform that cares about customers.
A platform that lets you see a preview of the product BEFORE you pay.
A platform that doesn't let people double charge you via surprise PPV paywalls.
A platform that at a minimum, has a review system so customers don't get ripped off.
A platform that lets users download the videos THEY PAID FOR.