My knowledge about accessing Netflix via VPN is limited, so I can't comment any more about that, but, as an experiment, I went through the new titles added to SG within the last 7 days (added since 28th Nov), and noticed that they all had one thing in common: they were all indexed as also available in the U.S. catalog.
Of course there are going to be titles common to both countries, especially ones which Netflix has global licenses for, and while I can't claim to have checked every single one of these newly added titles, it does seem that every title I have tried accessing from UNOGS that is not truly viewable here in Singapore does show up as available in the U.S.
Most telling is The Office (U.S.) series, known for being available only on Netflix US and Canada, is showing up on this site as available for SG (and several other countries), https://unogs.com/title/70136120
Another is Dexter, which I believe is also not available on Netflix outside of U.S., but showing up on UNOGS as available in several countries, https://unogs.com/title/70136126
My theory is, for some reason, the titles recently added to SG (and perhaps even the other countries that seemingly share the above 2 titles I quoted as examples) are actually pulled from the U.S. catalog. Perhaps this may be an issue to do with the VPN provider's servers, but this is just my wild guess as I earlier admitted, I know very little about the workings of VPNs.
Sorry for the wall of text.