Looking back to my post from 4 years ago, it looks like the 0-100kph time was far better than the posted 4.7sec. Back then, Road & Track had a joint venture test with Le Moniteur Automobile. That 0-60mph time (4.6s) alongside the Jag XJ220's 4.8s (which did the 1km sprint in 22sec) were ridiculously conservative estimates. But the 90s were complicated, even some 1km times, like say the Ferrari F40's 19.9 and the Lamborghini Diablo's 20.7, were actually liberal.
If you think about it, the 90s and even the 2000s were not much better than the 60s. They didn't have advanced stopwatches to keep track of speed and distance like today. I think the 3.6sec 0-60mph time (for the Ruf BTR) is far more accurate than the 4.6sec time, considering not only the 1km time, but also considering the gap in between 400-1000m; it did the 400m mark in 11.9s.
In addition to that, the 0-100mph time of 8.3sec is more consistent with the 11.9 and 21.0 numbers posted for the quarter-mile and full-kilometer miles, than the 9.7sec (let alone the 11.7sec) one. Also, I believe Ruf underrated the BTR in the same way they did with the CTR.