This shot was used because we needed to shoot both characters, as well as being able to see the writing without the light reflections. Black covered boards were used to stop reflections, while Perspex glass was used to see both characters.
The reflection of both characters on top of the writing increased tension. The pens squeak was used to emphasize tension and horror. Hollywood certainly comes across many obstacles as these and has to work around them. This may then alter the shot and cause consequences for the film.