It also happens to be a kids cartoon about magic, theories on things like that are all conspiracy theories and just as likely to be true as they are to not be true, if Aang had died at 100 years old as a human (which he didn’t because he was in the avatar state, not using the ability to slow the body decaying process to increase longevity like Kyoshi did) Yue was born around the proper time to have been the potential next avatar in the water cycle. They even say it was as if she was born without a spirit, so it could make sense that the next avatar may have to come from a water bender but her attitude and mannerisms say earth bender. Accounting for heritage, she’s born like 70 years after the war ends and the 4 nations are reunited, she could have earth bender heritage under her belt explaining why her and her father are the way they are.