Superliminal demo reel (portal to another level?)

Hello all!

I just watched the demo reel for Superliminal, a new upcoming game listed in the Epic store.

At one point in the demo there is a video clip of a bouncy house falling down in the middle of the level. A door is attached to one of the walls of the bouncy house that the player can walk through and END UP IN ANOTHER (most likely) level?.

Can this be done by streaming another level via that opening?

Any ideas would be greatly appreciated.