As mentioned in the other path, it is partly about tripping people up.
The diplomat already provided a list of all known foreign nationals that is supposed to be kept somewhat up to date. If foreign nationals are known that aren't on that list, it raises a red flag.
Why didn't you mention you banged this person? Why are you doing business with that person? Were the questions that this third person asked pressing enough that they should have been added to the list?
It is one of those things that makes perfect sense if you have even a basic understanding of these kinds of processes but that makes for a good narrative for the masses who don't.
