It's understandable to frame it in this way, and there are legitimate predators who take advantage of people in those environments. The common case is more prosaic: addicts are often codependent and will seek romantic companionship amongst each other, especially in close personal environments like that. Starting a relationship early on in the recovery process is a common (yet tempting) mistake and conventional wisdom warns against it, which is why the phrase exists.

[I spent a few years in the orbit of 12 step programs in my youth]

I don't think it needs to be that sinister; people tend to form relationships with those they feel emotionally close to, and there's probably a pretty rapid onset of intimacy in support groups like that.

I'm not saying there aren't predators, mind you, I just don't think that every relationship there stems from one person trying to take advantage of another.

Also... there is a severely reduced dating pool for someone actively in the middle of addiction recovery. If I had met a girl when I was single who said “I’m a recovering X addict with 32 days sober” I most likely would have not been very romantically interested. And if I was, it would be hard to connect with something when I have no experience of something so dominant in her life.

Thirteenth stepping is common enough to have a name, but the other side of that is that people in every AA group I've been in are extremely protective of newcomers. Thirteenth stepping a newcomer is a surefire way to get castigated by your fellow AAs.

In fact, I've seen three people ever asked to stop coming to a meeting, and all three were for thirteenth-stepping or similar. Being asked to stop coming may not seem serious, but for some perspective: the third tradition of AA is "The only requirement for membership is a desire to stop drinking." People show up disruptively drunk or tripping and don't get kicked out. A large portion of our membership have spent time in jail for violent crimes. Before these things were accepted in society at large, people of color and gays were accepted into meetings. We take the third tradition very seriously--the only way someone is asked to leave is if there's justification from the first tradition ("Our common welfare comes first") so you have to be seriously impacting the welfare of other people in the group before you'll be asked to not come back.

I'll also add that there are resources available to protect people. There are tons of women-only meetings and most areas have LGBT meetings as well. It's also explicitly not against any traditions to involve law enforcement if sexual harassment, stalking, etc. occur--there's a safety card which explicitly announces this and it's read at the beginning of many meetings.

When people get more sober time, dating becomes more accepted--generally after a year. But generally this is done with strong admonishments to put the sobriety of both parties first, and we still look out for each others' safety.

I don't look at AA with rose-tinted glasses. It's a human program and it's imperfect. Certainly as an atheist I wish there was a lot less god nonsense. But the flipside is that I'd probably be dead if I were still drinking, and instead I'm 20 months sober and doing really well. Certainly 13th stepping is a problem, but it's a problem which many groups deal with fairly well, and I wouldn't want anyone to not get help because they are afraid of being 13th stepped.

"I have a problem and I want to share it with you."