It's useful in specific situations, not a universal rule. Double cleansing (an oil-based cleanser first to dissolve sunscreen/makeup/sebum, then a water-based cleanser) genuinely helps if you wear sunscreen daily (you should) or makeup, because those aren't fully removed by a quick water-based wash.
If you're bare-faced and didn't wear SPF that day, a single gentle cleanse is fine — over-washing can compromise your barrier. So: PM after sunscreen/makeup, double cleanse is worthwhile; AM, a single gentle cleanse (or just water) is plenty. Match it to what's actually on your skin, not to a step count.