Yes, an unpowered LED emits no light. But an OLED that's barely on, for example at uniform 1% grey looks like crap because of the noise. People describe this

Yes, an unpowered LED emits no light. But an OLED that's barely on, for example at uniform 1% grey looks like crap because of the noise. People describe this as a "texture" or "banding". It's the consequence of trying to drive millions of individual semiconductor devices to the same emissive power. At higher brightness you can't notice the noise.