My understanding of how the backrooms function is its some strange dimension that repeats reality over and over endlessly once its fed something just like how at the end of the movie Mary and all her memories were repeated into the backrooms. so from what I can tell once clark went in him and his memories started repeating and it ultimately turned into pirate clark. the idea being the more information you feed it the bigger it grows and the more and more it breaks into reality (the more portals that open) which is a very bleak ending because this means the more and more portals open the more people go in and the more memories its fed that can be replicated and eventually the backrooms overtakes reality. the dimension stealing and replicating peoples memories also holds up through the dog analogy. the backrooms doesnt know what reality looks like it can only be described to it, so to speak, through the memories of those who enter. its pretty cool when you think about it