I guess so. I've had two previous fitbits and I believe those track every second during exercise and every five minutes otherwise. But those watches would still only get 5-7 days of battery life.

Hence my skepticism that this feature can be offered and still get 4x more life than that.

it's e-paper (reflective lcd), so it does draw some power at all times, but lower without an always on backlight

I don't know if it's the same thing, but Sharp Memory LCD has low quiescent consumption and memory somehow built into the display.

https://sharpdevices.com/memory-lcd/