The "Pinch Post" comes directly from the Triangle Offensive, developed by NBA legend Tex Winter. While many basketball fans would associate the Triangle Offense with the Chicago Bulls and LA Lakers teams of the 1990 and early 2000's, its concepts are still alive and well in the NBA.
One of the focal points of these actions to occupying defenders. A defender cannot effectively guard two consecutive actions. Forcing players to defend consecutive or concurrent actions is nearly impossible to guard when the offense makes the correct read.