This is good advice. I remember the first time it happened to me as a new driver many years ago. I had a Pontiac Astre, rear-wheel drive with studded rear tires. Took off in the snow (slowly, fortunately), lightly touched the brakes, and the front wheels promptly locked up while the rear wheels, with all that traction, kept pushing the car along. Pressing harder on the brake eventually locked the rear wheels and I stopped, but shifting into neutral would have been the better solution. Note: this is more likely to happen when the engine is cold and idling fast. It's a good reason to let it warm up until the idle speed drops to normal.