Myself I have always thought of a triangle over the court. So I agree with it through my experience. However there are two things:
1) The data window here is too narrow. It's needs to be tracked with more than one pro player over a longer period of time.
2) Does this information apply to recreational players?
Pros hit with a level of pace and spin that will certainly make a shorter ball penetrate more deeply in the court (Pseudo Deep) than recreational players can generate.
Babolat Pure Drive "Black" (1/4) w/ Skin Feel replacment grip.
Solinco Tour Bite 16 @ 55 and Tourna Grip XL