I think their niche are existing G-Shock fans who want fitness tracking
I am of the understanding that much of the allure of the G-Shock is the 2-15 year battery life. This offering takes what I assume is one of the biggest benefits of a G-Shock and trades it for fitness tracking capabilities that are available through many other solutions that offer much better battery life.
How? I can't wait to order one, there's nothing quite like it on the market. Garmin has a similar watch but it's bigger and heavier - I'm not interested in that.
The fact that this G-Shock is smaller and thinner likely explains the shorter battery life. It's definitely a trade-off that some people (like you) are interested in making. I have a Garmin Fenix 5 and that thing is HUGE.
Garmin instinct 2 is smaller and similar price, and battery lasts about a month