Obviously if Bruno Sacco is involved, a design decision is not trivial. Under scrutiny here is the decision to make the lower edge of the 1991 Mercedes S-class sideglass sag by a very small amount.
What effect did it achieve and would the car be better off without it? Here are four photos to show the effect of a straight lower window line. Obviously this sag is a deliberate choice. By removing it we can see what effect it was supposed to have. I think.