Huh, well that's it exactly. There's an almost innocent etherealness to it. These monsters aren't here for you, to interact with you, they're just here and this is what they look like. You don't understand their motives, or really anything about them, because they're far too other, you only perceive the similarities, and that's where the terror is. You get the sense you're seeing something secret, because if they did notice you, you feel like it would be a very different interaction.

Oohh, this was the reference/association my brainhole couldn't trace!

Too creepy & homey at the same time.