I think it’s as crazy as the simulation runs for aeons, but probably only from the perspective of those inside it. But these “shadow worlds” only exist for a brief time for the maker, who “enter” to experience the present day scenario. But yeah, that doesn’t fit with everyone only NOW realising everyone’s synchronised when it comes to thinking up random numbers. So… I think it’s another example of scrutiny unravelling a great idea, but Doctor Who is hardly known for its robust sci-fi… so I can let it slide.