they do that to get around the solenoid and actual fan replacement costs which are very high to fool the computer so no codes. Only difference now with these other blades would be when the clutch locks, it will cool a lot more including a lot of the engine bay where the rad mounted fans can't help. and the advantage? no more worry if the e-fan will die in the worst spot and no more burned up relays or a 30 amp extra load at idle on the ALT when it is trying to maintain the AC blower, headlights, wipers, brakelights etc. that was the huge advantage of the hydro fan when it came out.