The whole point of the comment is that time outside matters more than what is done outside. I don't know the degree to which this is true but if you're going to

The whole point of the comment is that time outside matters more than what is done outside. I don't know the degree to which this is true but if you're going to watch something anyway, doing it outside instead of inside seems like not a bad plan. I don't think they intended anything by specifying tv and you could replace it with reading, board games, drawing, any activity commonly done inside.