This is one of the more odd Silent Hills theories we've heard so far.
The very title of Silent Hills seems to suggest that there is more than one location (or world?) affected by the creepy phenomena we've seen in the series to date. In fact, that's something the core franchise has already demonstrated.
The question of what causes these phenomena to break through into the world is one the canon has left deliberately ambiguous. But maybe Silent Hills will answer that, by explaining that Silent Hill itself is a living entity trying to break into our world by way of game developers.
So you remember Youtuber Dreamcast Guy, right? he gave us a pretty good break down of P.T. in which he argued that Silent Hills will star a gamer and concern multiple dimensions.
While fans were pretty pleased with the idea of multiple dimensions, the whole "gamer" thing didn't go over so well. Well, Dreamcast Guy is back with a new theory. He now agrees that a gamer is unlikely, but his new idea has a similar theme of reality and game blurring together.
I certainly feel like Silent Hills will concern a different reality (or perspective, depending on where you stand in the great big what-is-Silent-Hill-about debate), but I'm not sure I believe it will take an Alan Wake style approach. That seems too derivative for creatives like Hideo Kojima and Guillermo del Toro.
What I like about all these videos though is how much information and speculation are being pulled out of P.T. If this is the kind of engagement the full game gets, then Kojima and del Toro can really go nuts rather than speaking to the lowest common denominator, as many games do.