It is interesting that you chose that particular nit to pick. I have pointed out repeatedly and in many fora that it is rare to be able to shoot with a truly level stick. The last time I pointed that out -- about a week ago -- I also pointed out how it was possible to play with negative elevation and get swerve to the left with right side spin. Byrne has a relatively practical negative elevation shot in his 350 shots book, I believe.We both know there is no such thing as a level draw stroke....
I deliberately chose the wording I did to make the point more strongly. The qualification, "as level as possible" reduces the force of the statement.
Swerve and jumping are the major reasons for not elevating more than you are forced to. There are some others. I suspect Dr. Dave covers them on his web page.