I 100% agree with the sentiment here, almost exactly what I said to my wife about the perfect blend; it’s uniquely Doctor Who.
However, the gravity bit is almost certainly not unnecessary, because they kept saying “mavity” for the rest of the episode. It’s a clue. This is no longer our universe, shenanigans are already afoot. There’s definitely a reset coming at some point, because it’s not going to be “mavity” for the rest of the show’s life.
And the Doctor is aware (his facial expressions whenever “mavity” was said, and he said “gravity” near the end), but Donna isn’t (she didn’t know what he meant when he said “gravity” near the end)