Yes, it is a small error and a small intrusion, but it still matters. Even if no one objects, it still matters. First, it matters because it is a breach of trust, since the DM is not trusting the player to play his character in an interesting fashion. This leads to players who tend to be passive, rather than active participants in the play. All good DMs seek to entertain their players. But it's a breakthrough in the understanding of a player when they realize that it is there job to entertain each other and the DM, and that they can employ many of the same techniques that the DM employs. Secondly, it is a breach of confidence, since you as the DM are not trusting yourself to be able to do the harder work of showing rather than copping out and just telling. Thirdly, it is a failure of the DMing art, since it is perfectly possible to leave a player anxious and worried regarding the outcome of an encounter and so engage the player directly. It's perfectly possible to describe a spooky environment in such a way that the player begins to feel faint palpitations and stress, often eliciting comments like, "I've got a bad feeling about this." and so forth. You don't need to tell the player something is frightening, and to do so is like telling the player something is funny. Saying something is frightening or funny is never as fully satisfying as the thing being frightening or funny.