DXOMark results for GH3

I think you mixed up some E-M5 data with GH3. GH3 has 12.35 DR at 94 (measured) ISO, not E-M5. See how similar they are that you didn't even notice?

Then for the next round I suggest to bring other camera with the same sensor in the equation, E-PM2 for example.
http://www.dxomark.com/index.php/Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/%28appareil1%29/840|0/%28brand%29/Olympus/%28appareil2%29/842|0/%28brand2%29/Panasonic/%28appareil3%29/793|0/%28brand3%29/Olympus
Click on measurements, then on SNR 18% or Tonal range, you will see charts where E-PM2 deviates from E-M5 more than GH3 deviates from E-M5.

You wouldn't suggest that E-M5 and E-PM2 have different sensors, would you? It's just different sensor tweaking.
Panasonic made base ISO slightly lower, but they effectively lost ISO 25600, it's because the tweaks don't give free lunch.