Joseph, Giles said that the WTS registered as an NGO for the sole purpose of gaining access to the UN library. The librarian said "Grounds passes are obtained by submitting requests on "raised letterhead" from the institution you represent, and these requests must present evidence that there is a legitimate "research need" that will be met by library access; generally "one, or two, or three" persons only from that institution may use the grounds pass. Grounds passes are not issued when one becomes affiliated with the DPI because the DPI does not issue grounds passes; the security department of the library issues those. NGOs affiliated with the DPI would still have to submit a request for a grounds pass on raised letterhead, but the fact of the affiliation would stand as evidence of a legitimate research need, so no further evidence would be necessary."
That says to me, that the WTS still had to submit a request for library access even AFTER becoming an NGO, they just didn't have to do a little extra legwork by supplying evidence of the need for that access. Being an NGO didn't really contribute at all to the library pass.
Another thing to remember that although they didn't have to provide proof of need for the library pass, as an NGO they DID have to submit examples of articles promoting UN propaganda. I would think for the sake of their beliefs they would rather supply the proof needed to get library access rather than the meeting the criteria of being an NGO associated with the DPI.