Why is usually that important? If a unidirectional bezel is knocked and accidentally moved over a dive, it may possibly only Show an extended underwater time. Meaning the wearer will overestimate as opposed to underestimate immersion time, and in conditions that need decompression stops, this can be a make-it-or-split-it issue https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/