Did you see the TCM presentation about Night Moves? The main point was that the film was about the detective and what he is going through. The overall who-done-it part of the plot is like a MacGuffin in a Hitchcock film. Thus I don't think it was done to be confusing because "we're much too cool,,,, etc.), but instead because "clear resolution" was not the main reason for making the film in the first place.
Also, there are noir\crime films from the classic-noir era that were confusing and had untidy endings. Films like the 40s The Big Sleep were confusing and had con