Why is usually that important? If a unidirectional bezel is knocked and unintentionally moved on the dive, it might only Show a longer underwater time. Which means the wearer will overestimate rather then undervalue immersion time, As well as in cases that require decompression stops, This may be a make-it-or-split-it https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/