No, they used Coggan’s 20-minute test to determine the power the athletes had to ride at, i. e. they subtracted the usual 5 %. Have a look at the study and the discussion in the corresponding forum thread. As you can see from Figure 1 in the article, only a minority of athletes is able to hold the FTP (determined by the 20-minute test) for longer than 60 minutes. (The boxes correspond to +/- 25 % of the athletes above/below the average.)