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You're right. For Gamma > 1, the two methods give different results. For Gamma <= 1, they are the same. It seems that the Exposure Adjustment Gamma setting moves the black point. I don't think it should do that. I wonder if that's a bug.
I suspect he used the Levels adjustment for his comparison. He doesn't explain very well what, if anything, he did in DPP before bringing the images into PS. I think you need very dark (almost lenscap-on dark) images to show what he is showing.
These noise comparison tests are always tricky. For one thing, real ISO can differ from indicated ISO among camera models. If a manufacturer is "cheating" with a real ISO that is less than indicated, the noise results can be impacted. There is also a relationship to dynamic range and the way the manufacturer is artificially setting the noise/black floor. I can, for example, raise the Blacks slider in Lightroom to eliminate most, if not all, shadow noise. The question is how much good detail did I lose in that process?