Distance is the length of the path travelled
displacement is the shortest length of the path travelled
distance does not have direction, hence, it is a scalar quantity
displacement has direction, hence, it is a vector quantity
The reason both of these are valid scientific hypotheses is because A) scientists with different educational backgrounds may put forth different hypotheses to explain the same data.
This approach in science is vital in making progress and has helped to explain many phenomena in the past. When scientists explain data using different approaches, they come to a more comprehensive conclusion.
