You still get me wrong. Thanks to your explanations and to my personal knowledge about this topic (programming for 28 years now; PhD in CS/numerics/HPC) I now fully understand the technical details about the current implementation of FD. The problem I see is that the average Python user does and should not care about such details.

I talked to a bunch of people (n=7) here at the company where I also give Python courses from time to time. I asked them two questions:
1. Is this behavior of FD what you would expect?
2. Given the current behavior of FD, what use cases do you see?

The answers were always the same (and I tend to agree):
1. No.
2. No idea.

All of you seem to answer the first questions with yes, but what's your answer to the second question? What would you recommend your 10-year-old son or your 62-year-old mother to do with the current FD operator?