Same thing about Roy and Harden. He runs the offense better from the SG position than the point. You can have a high usage rate and have the offense revolve around you in a way at the SG position that mimics the action that a point guard creates but it typically puts the ball into action at different spots in the half court as opposed to your general point guard sets. Why? Because off-ball action early in the set to put them in their most effective spots with regularity are just more effective than them simply walking the ball up the floor and working from scratch. (dumbed down version)
Both of those guys ran the entire offense from the SG spot. Best quick example that a lot of people can draw from.
Russell will not be a traditional pound the ball PG on the Lakers. He and Clarkson will both be sharing point duties where Russell will be playing off the ball a lot as well. The positions are just titles with this Lakers team.