I think some of the confusion comes from the early days of development of the websites and using CGI stanley. The US State Department always had their own website, and the various consulates around the world also had autonomous websites that were supposed to be under the auspices of the US State Department, but truly by all appearances many of those websites appear to run rouge.
As you know, the US traveldocs website limped into existence and remains a confusing existence to the public. It's far from user friendly, and one must wonder whether the data is secure. Certainly the website isn't stable, and there is no way to know whether other US departments are even sharing that information.
Now, it appears the NVC and US traveldocs have some handshaking going on, or at least that seems to be the intention. For example, the flow is:
1. Petitioner submits I-130 application, fees, and supporting paperwork to the USCIS.
2. USCIS reviews and approves, then sends to the NVC
3. NVC contacts petitioner and beneficiary with GUZ number, request to pay AOS and IV fees
4. Several days later the NVC provides a new GZO case number. This is the electronic case number
5. After paying the fees, the applicant (beneficiary) completes the DS-260 online at the CEAC website and submits
6. Petitioner submits i-864 and supporting documents in electronic format to nvc email
7. NVC acknowledges receipt of i-864, and states they will review and reply within 30-days of their receipt
8. After approval of DS-260 and I-864, the NVC forwards the approved paperwork to the consulate.
9 . The Consulate sends letter to applicant
10. At this point, the applicant should initiate process in US traveldocs