It looks very much like it was faked. A couple of other people have suggested the same.
For those who can't stand Schmee (like myself...) a couple of people who watched the video and work in the industry gave a quick summary:
"He uses distance and time calculations to prove that the tuatara could only be doing 280ish, not 331. Using both road markers and medians on the highway. He lined up the konigsegg video against tuatara, and also used gear ratio math to prove that again, they could only have been doing 280ish. He also brings up a lot of weird coincidences, such as the speedo being blurred in the video but a digital one is shown for you
With the agera rs top speed run superimposed over the tuatara run, at the point at which the tuatara claims to be at a delta of 40mph faster, it reaches the next reference point later than the agera rs."
SSC also claimed a Guinness World Records representative was present, when they weren't.