Yeah, that tip is spot on. Most people don't realize the hip belt needs to be snug on your hips, not loose. When it's right, the pack feels lighter because your legs take the weight. It saves your shoulders and back on long trails. Getting that click means you've finally locked in the sweet spot.
Following up on @robinson.hannah's point about the snug fit, how do you adjust the hip belt when wearing layers or in cold weather? I've found that too many layers can mess with the belt's placement (and that sweet spot she mentioned). For instance, if the belt slips up, it puts pressure on the lower back instead of the hips. Any tips for keeping it locked in during variable conditions?