In many trailers it was sold as a film with a solemn atmosphere, long sequences and shots always from the murderer's perspective... And then we see how the film breaks with that technique.
Still, I don't think it's a big deal and will ruin the experience. As I said, I had a good time watching it.

I also enjoyed it a lot, but I feel that it was very pretentious in its marketing campaign... Still, I agree with what you said: It would have worked better as a short film.