This head on swivel concept means you are taking your eyes of where you are going ... I prefer to stick with situational awareness. Be aware of where you are skiing and how fast, be aware of the terrain and take both into account so you stay in control and can react quickly if needed. If I am skiing down a hill, why do I need to look back, if I am traversing across a hill different story but even then I have a wide field of vision and situational awareness.Yes but ahead could mean one second behind, and one second even, and then one second in front - this would indicate that crossing skier was out of control. They have the visual field and If someone comes across the hill out of visual range and then moves ahead by feet, I don't buy it, the original uphill skier is the reckless one even if he jumps a head of the other skier!
More experienced skiers need to be vigilant and be aware of potential situations that are developing. Many of the new skiers on the hill don't have the experience to execute the code. New skiers are often able to ski fast. Head on a swivel makes sense. If someone jumps out after taking a break on the trail it's their fault, but good skiers don't rely on predictability. It's called protect yourself at all times.
Ultimately here is some very basic advice that actually holds true lol