That's why I would expect them to use an OLED display and a dark watch face. Anything else is simply too power hungry.
The point is, these watches have something like 6 independent motors, and each press of a button makes the dials fast forward to a different position, depending on the required function : Chrono, timer, Radio signal reception for atomic clock adjustment and so on. And it still manages to function without a battery - only on light power.