It's probably based on the belief that riunning freewheeling hubs on a seires helps fuel economy. if you remove the spinning buts in the front axle then you will have less weight to get spinning, thus making it accelerate quicker and use less fuel.
You will harldy notcie any saving and as said it won't compensate you for the cost of getting towed out of a ditch, if you don't smash the rear diff or transfer box first.
