Is the EM5’s Miss-Stated ISO concerning to you?

Gee, Don, I never would have guessed that on my own. Where have you been all my life ? My questions were in relation to sensor-level Exposure (you know, the real deal, just like "downtown") in order to assess RAW-level image-file channel-scaling applied by different cameras.

Not sure where you get "brightness" out of the above - but Westlake's reference to the "Brightness" control of Adobe ACR/LR through versions 6.x/7.x concerns a user-control that Adobe states modifies the gamma-correction constant applied to RAW-processed images. The net effect of tweaking that control is to modify the (midtone) Signal to (image) Noise Ratio of the particular DPR SCT RAW thumbnail. Thus, such tweaking results in a deviation from what would be a truly equal comparison.