That mode has the motion blur issue you mention in your post. But DxO did not measure the performance of the Dragon sensor in that mode.
As, I understand it, in the standard mode of operation, multiple exposures are also performed to make 1 video frame. This is not for HDR reasons per se
(HDR mode, as I understand it, would involve combining shots taken at different
exposure settings and then tone mapping the result into a more usable DR), but rather for temporal NR. This temporal NR produces the extremely high measured DR, unexpected in a APS-H 19MP camera.
If I'm correct in this understanding, then motion blur could still be an issue.