New Releases are movies that are new in the year and Recently Added are movies that may not be that new but have only just been added to Netflix.
But yeah I guess you could say that some of the Recently Added movies could be in New Releases category and vice versa
Yeah the comments above me were what I was thinking but rubes makes a point like new releases (movies/tv that came out that year) objectively have to be recently added... strange world
Recently added it can be an old series