[vintermann]

The web series and the film also defaulted to a very SCPified generic horror formula with conspiracy, "containment" and monster jumpscares.

But the original element that set backrooms/liminal spaces apart wasn't what was in them, but what wasn't. Sure it's creepy to be all alone, you may be afraid to get jumped, but you aren't. Some of the backrooms-inspired video games stay true to this concept.

So point is, the "Backrooms" film author may be an outsider, but he sticks to a very well-tried formula - one mainstream authors probably avoid for being too cliche more than anything.