I feel like that’s the same underlying issue: The requirements are not understood upfront.

Actually on most of these failed projects the requirements of the original customer were pretty clear. But the developers tried to go far beyond those original requirements. It is fair to say that the future requirements were not well understood.

the alternative is building a prototype, which you’re allowed to throw away afterwards

Lol I've done many prototypes. The problem is that management sees them and says "oh, so we're finished with the project already? Yay!"