Unchecking Emit Light should indeed mean "turn the light off" - here's how it looks in Max, working as expected:
Self Illumination in the Corona Mtl always casts light into the scene, which is where the Light material with Emit Light off comes in :)
I think Cinemike was just pointing out that the result with Emit Light on and off does in fact change, but rather than turning off the emitted light, it simply starts acting the same as a CoronaMtl with Self Illumination enabled (based on what is seen in the noise).