Yeah but if the OLED screen has to display black (RGB 000), it turns off the diodes completely. But as you said, most dark modes have a dark grey background which doesn’t do shit (jerboa has a black option btw)

For oleds, it makes a difference and not an insignificant number of smartphones today use OLED screens.

However, if the microwatt-hour of battery saved by browsing a shitty website of a shitty company for a few minutes saves the planet is another story…