Programminst avoid using absolute paths, because it makes nodes stiffly dependent on their scene tree allocation. If You were to decide some day, that You want player to be child of a different node, or You would want to add node inbetween nodes - You will have to change all of the absolute paths in whole your code, because they will start to crash your project.
Generally You want to call and change values of other nodes at short distances ( parent - child ), but when you want to pass information along whooole scene tree, like in your example : use signals !!