If I understand the original UN debacle correctly, the problem wasn't because they were/are an NGO, but what they had to do to apply for association with DPI, which requires that they accept the charter and principles of the UN. And after the article in the Guardian came out, they only disassociated themselves from the DPI.
Being an NGO was what required acceptance of the UN charter. 'Association with the DPI' and 'NGO status' in this context are synonymous. It is important to have the facts when making claims of a scandal.