Why is the fact critical? If a unidirectional bezel is knocked and unintentionally moved on a dive, it may only Show a longer underwater time. Meaning the wearer will overestimate instead of undervalue immersion time, As well as in situations that involve decompression stops, this can be a make-it-or-split-it issue https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/