I don't think they are honestly. They may know some of the intracacies and difficulties of their specific problem and then project that it will be that difficult to make progress in other subdomains. Which is probably true, but they also tend to underestimate the efforts other groups are putting in and the progress that can happen in other subdomains, which isn't always linear. So imo, they aren't really qualified to give an accurate prediction because very few have actually even studied the problem. I'd trust the people who have actually studied the problem, these are AGI experts and tend to be much more optimistic than the AI field overall.