Absolutely this. No recruiter with any kind of sense is going to go "Hey, does your boss know you're on Twitter all day? That's sooooo inappropriate. Imma tell him! Also, when he fires you, I can pair you up with a great opportunity!" If they have a job that needs filling, and they think you're a fit, they won't care that you're already employed. In fact, as they get a percentage of your salary if you sign, they like it that you have some bargaining power.

This is cozying up to the employer, telling them that they have a problem employee, and presenting themselves as a solution to that problem.