A new mishnah! The presumption of ownership is dependent on where the land that is under discussion is located - specifically, Judea vs. the Galilee. Which also teaches the challenges of travel in the time of the Tannaim. Also, what if a person flees his property, and someone else comes in to take possession of the place? The sages say nobody can take possession of the property of someone who fled his house, using someone fleeing as the extreme case that might explain why someone is trying to take possession of the home in any case.