I recently had a quick peek about this feature .. it piqued my interest!

Seems multiple images are taken, processed and a single raw file is output.
IQ in the images shown Mark, look very good for a multi shot blended image.

I assumed that the softwareyness of the idea behind the feature may have been something like extended lower ISO values.
In those lower than native ISO settings, what the camera makers actually do is capture the image at the base ISO, then apply an exposure compensation appropriate to the lo ISO requirement.

eg. say lowest native ISO on camera is 200, and the camera has a Lo1 setting that is -1 EV below that, the reason it's not called ISO100 is that it's not technically ISO100.
At this Lo1 ISO setting, camera is overexposed at ISO200 by +1Ev, and then in camera -1Ev is applied to give a psuedo ISO100 appropriate exposure.

So I was assuming that some nasty negative gain on ISO/exposure type operation may have been going on in camera to get a non hardware ND effect.
Multi shot seems like an interesting idea for it tho.