By the time people are in the room, most of what is going to happen has already been settled. Who was invited and who was not. What the invitation said the hour was for. Whether a senior leader will be there. Whether notes go somewhere. Whether saying no costs anything. Whether the materials arrived in a form everybody can read, two days ahead rather than two minutes ahead. People read all of that accurately and adjust what they are prepared to say, usually without deciding to.
This is why technique inside the room is the smaller half of the job. No facilitator, however skilled, can undo an invitation that asked people to reveal something, a note-taker whose summary reaches leadership without anyone being told, a room that can only be entered by a staircase, or a session scheduled in the one hour the interpreter is not available. Those are conditions, and a leader sets them, deliberately or by accident.
Two of them are worth naming out loud rather than managing quietly. The first is power. A staff member cannot leave a bad conversation with a director in the way a director can leave it. A temporary employee, a person on a performance plan, and a person whose accommodation request is still pending are each carrying something into the room that nobody else can see. Warmth does not dissolve that, and neither does an invitation to speak freely. What helps is naming the asymmetry, providing a route that does not run through you, and then behaving well the first time somebody uses it.
The second is the record. People calibrate what they say to what they think is being written down, and in the absence of information they assume the worst version. So say it: what the notes will carry, who receives them, whether anyone is named, what stays in the room. If leadership needs a summary, say so, and say what will be in it. Honest recording terms cost you a sentence and buy you the only thing that makes the hour worth holding.