That makes sense, especially if other celestial bodies function like Earth. In other words, what we perceive from Earth are celestial bodies according to how Earth wants mankind to perceive them. This makes the last chapter all the more confusing.
Da Vinci stated that the injured party in the universe update wasn't Earth, but rather the universe itself, a process that nullified lifeforms on every other celestial body. This implies that there are other lifeforms distinct from humans. Furthermore, Daybit implied in Lostbelt 7 that humans are a threat to the universe due to their undying will to survive.
If everything had gone according to Marisbury's plan, the FGO timeline would have effectively erased all universal lifeforms and celestial bodies except those of Earth.
While the existence of other Ultimate Ones in the FGO timeline can't be confirmed, the idea that celestial bodies host different life forms has already been established with them labelled as external factors unnecessary to mankind.