Yes, transflective screens consume MUCH less energy than a OLED/LCD or whatever display tech that these watches have that require backlights to function.
The Garmin works just fine without an active backlight (due to transflective) and has much fewer colors and worse resolution and worse refresh rate. It also does not have a touchscreen which also consumes lots of energy.
The modern smart watch advertises always on screens because it manages to get a day of battery life with a "good" display
All good points, though even the latest Forerunner 965, which has an AMOLED touch screen, gets 7 days of battery life in display-always-on mode, and 3 weeks in default mode (display turns off)^1
My Amazfit GTS 2 mini also manages 2 weeks on battery and it's got an OLED screen that I've set to always on, and it's got a touchscreen. And it's a small and light watch so the battery can't be that big.
I think the biggest battery waste is the full OS. Like the Garmins my watch doesn't have installable apps.
Ps Garmin also sells OLED touch models with long battery life. Like the venu
IME the OLED Garmins don't have that long of battery life if you have the display set to always-on. For me (Forerunner 265), it lasts maybe 3 days. Better than an Apple Watch, but not nearly as good as an Amazfit.
The Garmin works just fine without an active backlight (due to transflective) and has much fewer colors and worse resolution and worse refresh rate. It also does not have a touchscreen which also consumes lots of energy.
The modern smart watch advertises always on screens because it manages to get a day of battery life with a "good" display