"You have always had individual directors who begin in the advertising or commercial world, but they are probably exceptions rather than the traditional pattern"

This quote by Ann Macbeth suggests that while there have actually been some directors who have actually originated from the advertising or industrial world, this is not the traditional pattern. This implies that the standard pattern for directors is to come from a different background, such as film school or theatre. Macbeth is recommending that while there are exceptions to this pattern, they are not the standard. This could be interpreted as a suggestion that the standard path to becoming a director is still the most typical and effective path. It might also be viewed as a cautioning to aiming directors that they ought to not rely entirely on their advertising or industrial experience to get them into the movie industry. Rather, they ought to focus on developing their craft and developing their skills in order to end up being a successful director.