Pitching off the mound doesn't equate to how far you can throw a baseball. I know what Alan says, it may sound scientific, but it is not.
They are two different skill sets.
The Science and Art of Baseball Pitching 5.10
Height of release. The higher a ball can be released relative to the ground, the further it will go if it lands on ground of a similar level to that from which it was thrown. Thus, for a maximum distance throw, the release position should be at the correct angle with the ball at the highest point possible that can be attained in a movement that maintains good mechanics.
Rather than alter the angle of release, it is also a common variation to alter the height of release for different pitches. Curveballs often are released higher than fast balls. The extra height compensates for the gravitational pull that is of greater effect in curveballs (Atwater, 1977, 1982). The choice of modifying height or angle of release or both should be largely influenced by the preference of the pitcher. Because of individual variations in many factors between pitchers, it is of no benefit to advocate one over the other. Only experimentation and demonstrated better performances will indicate the appropriate coaching recommendation.
Velocity of release. The faster a ball is released, the further it will go. Because of changes in skill requirements, it may not be possible for a player to obtain similar release velocities over a wide range of release angles or heights. The human body is constructed so that forces and higher velocities can be developed better in some directions than in others.
What has this to do with pitching? Why talk about throwing a ball as far as possible when a pitcher needs actions that are controlled to perform in a certain way at the greatest velocity possible? The answer is a sneaky one. A common practice activity for pitchers is the "long-toss". The long-toss involves honing in on an elevated angle and maximized height of release. These are action components that do not exist in pitching a baseball. Pitching requires throwing down from a mound to a target at a set distance. It is not a maximum distance throw but is a maximum velocity throw. The only common characteristic between a pitch and long-toss is the attempt to achieve a maximum throwing velocity. However, even that differs between them. The preparation for a throw and pitch are not the same. The throw involves preparatory steps or hops whereas a pitch allows only one stride. Thus, the movements needed to accelerate the ball in a pitch (an exaggerated wind-up) are very different to that of a maximal throw (an exaggerated lean back after preparatory steps). Consequently, there is very little to nothing in common between a maximal throw, the long-toss, and a baseball pitch. The three release factors are different between the two.