Why is the fact critical? If a unidirectional bezel is knocked and unintentionally moved on the dive, it may only display an extended underwater time. Which means the wearer will overestimate as opposed to underestimate immersion time, and in cases that involve decompression stops, This may be a make-it-or-split-it variable https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/