If you've played MGS games before you'll notice that the difficulty in this demo was considerably toned down. Some enemies simply ignored snake when he was standing in plain view of them or when he made a bit of noise. Like when he dropped from the ledge to electro-knife that soldier. The soldier would've heard that in Snake-eater.

Kojima wanted to show everyone the features without the annoyance of getting killed at one point or having to interrupt a demonstration to kill off a guard that inadvertently spotted him. I wouldn't consider this demo to be a finished version of the normal difficulty by any means.