> "Trap" here means the deal is so good that they don't ever want to leave.

Yes. I know someone who has a huge rent controlled place in San Francisco and has had it for many decades. Probably worth like 10K/month if you rented it today. I don't know what his rent it, but he says it is so low that he'll never give it up. He no longer lives in San Francisco, lives elsewhere. The SF place gets used occasionally on weekends. So it remains empty, mostly unused, off the rental market because it would be insane to let it go. This is what rent control does. It's great for him and I don't blame him, I'd do the same too. But it's the wrong incentive.