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

That is exactly right , optimum exposure is what actually matters not an ISO setting in camera, it is unfortunate that DPreview does not take the time to demonstrate the best achievable results from a given camera . Though DXO use a very different interpretation of ISO , I do feel that their  particular way of calculating ISO gives a more          accurate indication of actual output images . I am not so sure that everyone takes the time to expose to achieve the maximum output quality . The fact that there are some 5 "standards" from which the manufacturers can choose how to determine the in camera ISO , seems to be an issue in itself ,though in latter years the main options from the digital camera makers seem to be as follows .

REI

The Recommended Exposure Index (REI) technique, new in the 2006 version of the standard, allows the manufacturer to specify a camera model’s EI choices arbitrarily . The choices are based solely on the manufacturer’s opinion of what EI values produce well-exposed sRGB images at the various sensor sensitivity settings. This is the only technique available under the standard for output formats that are not in the sRGB color space. This is also the only technique available under the standard when multi-zone metering (also called pattern metering) is used.

SOS

The Standard Output Specification (SOS) technique , also new in the 2006 version of the standard,effectively specifies that the average level in the sRGB image must be 18% gray plus or minus 1/3 stop when exposed per the EI with no exposure compensation . Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typically JPEG—and not to output files in raw image format. It is not applicable when multi-zone metering is used.

Saturation based

The saturation-based technique is closely related to the SOS technique, with the sRGB output level being measured at 100% white rather than 18% gray. The saturation-based value is effectively 0.704 times the SOS value .[18] Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typically TIFF—and not to output files in raw image format. It is not applicable when multi-zone metering is used.

http://www.dxomark.com/index.php/Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/(appareil1)/842|0/(brand)/Panasonic/(appareil2)/793|0/(brand2)/Olympus