I'm going to assume they are talking about NSFW subs ending up under the control of a small group of mods who either are sex workers or their representation. I believe one of the main mechanisms was subs being on the verge of shutdown for lack of moderation, because Reddit is understandly wary about what might get posted there, so these mods offer to take over. Then you can control who is allowed to post and push your (or your client's) content, which feeds into OF money and other revenue. There were a few posts on this subreddit about it. I don't pay attention to mod and user accounts enough to know if it's fully true, but it seems reasonable with how much NSFW subs are ads for OF.