I believe the proper interpretation is that, on an intentional walk, the catcher must be in the catcher's box when the pitcher initiates his delivery - i.e., at the Time Of Pitch (TOP).
If not during an intentional walk, the catcher is not confined to the box. Watch any MLB game and you will regularly see catcher's setup for an outside pitch with one foot well outside the catcher's box. Also, on a pitch out the catcher is free to setup outside the confines of the catcher's box or jump out of the box early.
JM
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