Packard did similar, single speed trans, torque convertor, lockup clutch. With a hybrid system it makes sense. VW was looking into similar, no torque convertor but the ICE would be used above 35mph or so.
I wonder how much abuse that Koenigsegg unit can take. From heat under slippage that is. How many hard pulls before something gets too warm? Then again, perhaps it just never stays in a high slippage region long enough--2.8 seconds 0-60, after all.