"It's a cheap trick to make me trust the interlocutor".

Hmmm. Different interlocutors can have different intentions. Some are going to have the intention to understand. Echoing what you believe the person said is not a 'cheap trick' when it comes to discussing ideas. I've been on both ends of conversations about singing, engineering and sailing, and one person says "what your saying is this" and the other person says: "No, that's not what I'm saying", with a correction that follows, and the chance for two-way understanding.