I like how you think mate, you got an Upvote. I had already think something similar but with the exception that I thought the world as like minecraft. lets suppose you are steve and the world around you is forming while you are walking, talking or anything you do as in minecraft, like in minecraft world, the memory of our world is limited, so to get the best and more efficient use of this memory, the cosmic entity, or let say the universe, or whatever you want to believe doesn't have the necessity of build the whole world at once, but while the avatar is moving and interacting with it, is also making it. I like to think this as the Schrodinger's cat, until the box gets open you cannot know what is happening within the box, now whatever you are, is your reality and beyond where your eyes cannot see don't exist. So enjoy the moment because nothing else exists until you see it.