I don’t think they mean passengers in row 50 put their bags in row 30.

I think it’s just that your eyes’s reach trends towards the front of the plane. If it’s busy when you try to stow away your bag, chances are you will prefer putting it in a meter towards the front of the plane (where you’re standing anyways, waiting for the person before you to stow away their bag) over cramming it in above your head, where the other bags already are.

Oh, people in row 40 routinely put their bag in row 8 if they can, because it means they might not have to check their bag if the plane runs out of space.