It is baffling to me that Apple still hasn't implemented this feature even on their top end "Pro" iPhones... but this feature by itself isn't enough for me to switch to Android full time.
Not months worth of battery saving like an eInk screen maybe but still enough to be insignificant compared to general "screen off" battery consumption.
They don't run regular Android though, with Google Play, just the open source version with some Chinese marketplace. I have followed one (now dead) e-ink phone on indiegogo (forgot the name, sorry), and they wrote that Google does not let (black-and-white) e-ink smartphones pass Android certification, because they cannot correctly display the colors in their apps. So they will never run Google Play, and there will never be just e-ink phone with built-in regular Android and Google Play, sadly.
There is a hacky way to get Google Play on the hisense phones, but... ugh. That's too much hackiness for me.