The Noct. is the name Nikon coined to reflect the actual indended purpose of the original nocturne 1.2 AI/S lens.
The 'neo-noct' is a term zealots coined in their failed attempt to liken the two (unrelated) lenses together ... based on a misunderstanding of each lens' intended purpose.
It is true that "Neo Noct" is no official Nikon designation.
But shortly after the release of that lens, a Brussels photographer (working at the main camera shop: PCH, rue du Midi) and (old) Noct owner showed me some night shots he made with both lenses, photos that were also published in a photo magazine. The comparison was rather in favour of the "neo noct", especially as far as flare is concerned. So the term is not undeserved.
Concerning the "other personality", I had a similar experience with the Noct : stopped down, and field curvature aside, it becomes a very sharp lens, while contrast always seems to be there (which is the biggest difference with the 50/1.2).
Bokeh-wise, the noct has a good reputation, at least compared to other fifties (I think the Zeiss MP is better though), but the neo noct seems to be even better. So once again, the designation is not inappropriate.
One thing is sure, none of these lenses have been designed to yield optimum results at test chart shooting (which probably triggered some howling in the marketing department). So what. Should I say "fortunately" ?