Nice to know that. I don’t play as Rath very often, but this will be useful nonetheless.
Hypothetically, the Blade wouldn’t spin and return to his hand on it’s own. He’d need some technical solution (like a forcefield) to either wield it from afar, or at least to pull it back in his hands. That means some part or even all of the motion of the blade during the throw is not provided by Rath himself, but by some technical gadget.
The amount of force delivered by one of his normal sword strikes would still be limited by his own strength, while any technical solution could easily provide more force.
But to be honest, to make any sense of it, we’d have to know how Battleborn’s Shield Tech actually works (from a lore standpoint).