Yeah, my first playthrough, I thought it was just NPCs chirping around me, but it turned out that they were real people! As players got more scarce, it was truly a special experience finding someone and going through parts of the game with them. I remember I encountered someone a few levels in and we somehow ended up together until we crawled up the snowy mountain, trying to keep each other from freezing. Not a single word spoken, yet this game has such powerful messaging.
I hope you get the opportunity to encounter your own Journey companion on a playthrough. :)