The game is either canceled or having an update plus the rooms are apparently in the game somewhere because at the end it says something you forgot and I found out that when you go to the shop at the beginning of the game there's boxes blocking the stairs and I noticed a yellow exit sign which might have something to do with the rooms or maybe the back doors
im surprised you found it. or you saw the thing kujy added at the normal ending and found it because of that. kinda crazy i didnt know attic access was there being a dev