After you discovered the new room, my friend and I decided to go back to previous versions we downloaded to investigate. As it turns out, this white room with a door is something that has appeared back in at least pa07_0005. We only checked the previous versions we had downloaded, so the only versions of the game we have confirmed its existence in is pa07_0005, pa07_0010, and pa07_0011. My opinion is that the door likely doesnt pertain to the issues caused by the current update, but that it may have some significance in the future. I saw a reputable source for VotV secrets on youtube reveal a similar hidden passage in a window of the pipe room after the maze, so its likely that whited out rooms with doors in them are going to be a common motif throughout the levels of the arg. It should be noted that the door was not, at least from my memory, the same door, but rather a copy of the Panopticon's prison doors.