The new handchecking rule came up in our local association meeting last night and there was debate on when this rule applies. Many thought it applies to the dribbler on the perimeter but not the post player. Others thought it applied to the post player only when they turn to face the basket.
But, when reading the case book 10.6.12 Situation B, it seems there is no distinction between a post player with their back to the basket or facing the basket, the new handchecking rule should apply. I would like to get clarification on when the post player becomes a ball handler and to when this rule applies? To me, it seems when the post player receives the ball, this rule is in effect and the defensive player needs to keep their hands and arms off of the post player, now ball handler.
The new rule pertains to any “ball handler/dribbler” regardless of their position on the court. There is no distinction between perimeter dribbler or a post player, nor is there any distinction as to the direction the post player is facing. The case book play you cited along with situation A are excellent examples to reference.
I would also agree with your definition of when any player has possession of the ball, they become a ball handler.