I never really liked the Palpatine broadcast, but I do like the idea of the message the spy gave Poe and Finn be a broadcast that was specifically meant for the First Order. If they all actually heard his voice, I can understand why they didn’t doubt the authenticity of the information.

As the film is now, Poe feels like a leaker telling fans the plot of the film.

JediPaxis: Somehow, Palpatine returned.

But like kraus said, I think it could also work as a replacement for Beaumont translating the Sith-language transmission. Because WHY are they transmitting a broadcast in a language that no one can understand?