The video’s second part is where practical, useful battery advice comes in. It suggests that you dim your phone’s brightness to save battery. High display brightness is one of the foremost reasons your iPhone battery drains faster than it should.
The light your phone emits directly affects the device’s battery; the brighter it is, the more battery it drains. Therefore, turning your brightness to the lowest level is one of the best ways to save battery short of shutting down your phone. You should also turn off your iPhone’s auto-brightness so it doesn’t automatically increase brightness when it senses light.
As comments on the video suggest, combining a low white point and low dimness makes it almost impossible to use your phone in anything other than absolute darkness. Even if the low white point theory was true, you might as well turn off your phone’s display completely to maximize battery savings.