now i might be wrong but that was a team time trial – still impressive but not an ITT
Yes, it was a group ride with support vehicles. I think 3 women rode the whole distance, and the others rode various sections as support.
There aren’t formal rules for something like the NC500, so you are comparing apples and oranges. Mark Beaumont was nominally riding solo and unsupported, but he mentions various people joining him on the road as support in his blog.
Things like the TD and HT have stricter rules about self support, but I guess you can still ride with other people, which could make a big difference mentally and physically, compared to a true individual TT.