I can only assume that ISO 800 was meant to serve as an example of the base ISO even though that would vary between cameras and profiles.What does ISO 800 have to do with the technology itself?
I guess it relates to C70 and C300 as concrete examples to get the highest range out of those 2 cameras.
DGO combines signal gain at low and high ISO.
Anything outside of that range can't use DGO and using an ISO between the range only shortens the range.
The highest dynamic range is typically the base ISO regardless of DGO.