Unrealistic optimism or just pure stupidity?

A while ago I've written a blog entry Where bad performance starts explaining that we as IT professionals should prevent customers from stupid requirements or at least strongly warn them that their desires will make much harder life both for customers and developers.

Some days ago I've spotted a nice estimate of a work task that takes the problem described above to the next level i.e. the core of problem is initiated even before the real project begins. Task was much bigger containing of many subtasks including:
1) three separated subtasks for three different reports. Each report was quite precisely explained;
2) a task formulated as follows: "Up to 20 reports defined more accurately in analysis phase". No more information was supplied, no more information was known to anyone.

So how do you think - what were the estimates for analysis and implementation? According to estimate analysis of each separated report should take 1, 2 and 3 workdays. Implementation estimate of each of them was 2, 3.5 and 3.5 workdays. And now the most interesting part: analysis and implementation of up to 20 unknown reports was estimated 15 days for analysis and 20 days for implementation.

So for known and quite precisely defined reports the average analysis and implementation work was estimated 2 and 3 days respectively for each report. BUT for completely unknown reports without any further information and/or restriction estimate was 0.75 days for analysis and 1 day for implementation.
BAHHH!
So what to think? What was thinking both analyst and programmer making such estimates? What was thinking PM allowing such estimates to be published and giving them to customer?Are they afraid of big numbers? Why are they being so optimistic? It is a real mystery...
I'd be afraid to give any estimate for such purely defined task at all. And if I'd give I'd take at least average or even probably maximum of other similar tasks and also warn my boss about quite big risk to give estimates of unknown tasks. Probably I've seen too much projects fail or at least delay due to overly optimistic estimates...