Every basketball shooter gets the "feel" for shooting a particular distance based on the thrust he must apply to the ball with his elbow, wrist and fingers. A player gets familiar with basketball travel in his home arena and practice facilities for long distance shooting.
Today's VMI formula tracks not only the schedule, but also includes significant shoot-around workouts between games.
In previous collegiate basketball studies, there was a 9% drop in three point percentage when road teams played at a "significantly" different altitude than their home court. All games and workouts form the touch of the shooter. When the touch must change to create a shorter shot by more than an inch, or a longer shot by the same or greater amount, then the VMI gauges that distance. If the team of outside shooters sports a minus VMI, then their normal thrust will place the ball a little short. If the team sports a plus VMI, then their typical thrust for that distance will be a little long. One and one half inches differential is enough to clip the rim and cause a miss.
How quickly and how many players adjust to that distance differential will affect the win percentages over the course of the NBA or College season. The greater the VMI, the greater the adjustment amount. The VMI is set up so that one inch of adjustment is gauged by a 4.00 VMI, 8.00 VMI would be 2 inches, etc.
There is not a superior side of zero VMI. Whether plus VMI or minus VMI, the adjustment is still necessary. Early in the season, the players' touch is not so cemented into a norm, it appears. This is most likely due to playing summer games, pre-season travel, and shoot-arounds anywhere they are available. After a couple months of the season, the teams are more settled into their home shoot around and home court, so the VMI seems to be more accurate later in the season.
