A couple of random thoughts...
The fog of war played a part, as likely did the comportment of the reporter. I still vividly recall Jerry Rivers’ spellbinding war narratives (did any of them actually come true?).
Of course there’s always the matter of the agenda of the NYT - that agenda being the advancement of the NYT.
As opposed to, say, Horace Greeley's New York Tribune.
Near as I can tell they were both on the same side, both in support of the Union and, generally, Republicans.
Who were the Democrat opposition newspapers, North or South, and what were they saying differently?
I don't know.