Originally Posted by SystemicAnomaly
Note that hitting an inside shot is different that hitting the inside of the ball. (Refer to the Wardlaw Directionals for the difference between an inside shot and an outside shot). One can still hit the outside of the ball when hitting an inside shot. The IO Fh gets it name because the player runs around a ball that would be an outside shot to his/her Bh in order to make it an inside shot on their Fh side instead. They are hitting the ball to the outside of the opponent -- hence they are hitting an inside-out shot. While the pros will often also hit the inside of the ball in this situation, it is not absolutely necessary in order to hit the IO shot.
Do you have a reference or source for that definition of I/O?