Doubtful, there are other, less-well known pay-for-content platforms than take a smaller percentage cut than onlyfans. It wouldn't make any sense for a launderer to use the most expensive platform.
Money laundering via platforms can work indirectly, where the dirty money is spent on advertising and other expenses used to drive business to legitimate vendors. Sex sells quite well so OnlyFans is a great platform for that kind of laundering, even if they take a higher cut. It might not matter anyway, if a dollar of dirty money drives more than a dollar of legitimate income that covers OF’s cut and their AI costs.
Mexican cartels absolutely use OF to launder massive quantities of money. They use OF because it's the one thats actually used by people. It's a lot easier and less suspicious to declare ridiculous high subscriber counts in OF that other platforms.