^^^They can "violate the directionals" (which are guidelines based on physics, not rules) because they can position themselves accordingly and have the hand skills the control the racquet face. At club player levels both of these skills may be lacking and hence the guidelines of the directionals are more appropriate.
I tweet - @ashtennis guru (no spaces)
I Shoot - www.flickr.com/photos/ashtennis guru/ (again no spaces! grrr)