Every time, no matter who says it, and no matter how crucial they say it is to the path.
As far as whether the letter was intended for the public, or for just HH's students, I would gather that it was intended for the public. He mentioned about things happening on social media, which by and large is public, and he sent his letter out through social media. His Son made the post public instead of just for friends, and also it was posted by his son to the group of dudjom rinpoche, so clearly for all whom are connected to HH Dudjom rinpoche.
I don't know, maybe we could stand to do a little good listening to the words of Dzogchen masters instead of people who are intellectual learned about Dzogchen. HH the Dudjom yangsi mentioned in a long life prayer written for Rinpoche that although all phenomena have dissolved for you, out of compassion you still benefit sentient beings. I fully believe that. In this dark age it's only beneficial to listen to authentic wisdom guides.