Best effort, and a foul line, are common elements in most

field events and should not be changed. In the throwing events, for example, not only does the best of six throws decide a winner (assuming you make the final three throws with a sufficient performance in the first three), there is both a foul line or ring that you may not cross, but also your implement must land within the marked sector. That's particularly evident in the hammer and weight throw, where the cage around the circle extends just out of the front of the sector for spectator protection. We have seen those implements hit the cage on the way out, resulting in a foul.
On approach speed, whether it be long or triple jump, as well as pole vault and javelin, it is about converting the speed of the approach into the jump or throw, i.e translating vertical force into the final effort. In order to do so, you must not only measure the length of your approach not to foul by crossing the line (which is perhaps a reason to penalize for fouls along the way), but also maintain sufficient control while still achieving maximum approach speed. Maybe Reese is simply more comfortable with a more gradual approach and an explosive effort at the end.