i didn't think much of it. i figured our perspective had them be upside down, but from theirs, everything was upside up all the time. kinda like someone on the opposite side of the globe would be upside down in relation to you, but upside up in relation to gravity
Viewing post in Question about the underground "upside down" scene
That's an interesting way to think about it, what with having the 3rd-person omniscient point of view. Though, I always thought the MC was meant to be a character for self-insertion? The scene does have "you" (the MC) perceiving the space as upside down, at least at first.
Maybe I'm just way overthinking this lol