>The manual says that ...... no original raw data is discarded.
I'm not sure that's what it means. My manual says (on page 86) that there is 'no effect on image quality' - I can't see any mention of the word data.
If lossless compressed doesn't discard any RAW data at all why did Nikon bother including the uncompressed option? The only reason I can think of is that an uncompressed NEF might be readable using future software, whereas a lossless compressed (or zipped) NEF might not.