Why is the fact vital? If a unidirectional bezel is knocked and unintentionally moved on a dive, it could only Screen a longer underwater time. Meaning the wearer will overestimate rather then undervalue immersion time, and in cases that have to have decompression stops, This may be a make-it-or-break-it aspect https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/