If you turn down the brightness, the background and text will become more similar in color, as both will move closer to black.

A dark background reduces total brightness without that effect.

Exactly. Contrast or, more precisely, the dynamic range we desire, is ruined by dimming displays enough not to cause pain and fatigue.

It's a dumb solution, and we may all safely ignore it, knowing it won't occur. "Dark mode" haters will just have to cope as dark becomes the default.