Response to eevee's Cohost post: "i don't think you should be allowed to name a difficulty "nightmare" if the monsters don't endlessly respawn. go to jail"
You select "nightmare" difficulty, and everything seems the same as normal difficulty at first. That's weird, you think, expecting that maybe some later part of the game is going to get difficult, or maybe the actual difficulty is that dying in certain ways is more punishing or something and you just haven't died in that way.
But then suddenly during a particularly intense section of the game with lots of monsters, your character is teleported to a bedroom, and a cutscene plays of them getting up and getting out of bed, and the rest of the game is spent doing mundane everyday tasks like driving to work or going grocery shopping. From this point on, monsters don't spawn at all. In fact, there never were any monsters. You were actually safe in your bed for the whole first part of the game, and the stuff with the monsters was all just a nightmare.