The purpose in Atlanta was to dredge up bad material on the Ramseys, it was not to investigate the case or advance the investigation one iota.

Consider the recently gained knowledge that FW had an excellent grasp of the note's text soon after the crime.

What do we have here? Something Patsy had recently learned of and it did not in any way lead Kane to ask a question such as 'do you have any opinion as to his memory skills based on incidents that you experienced with him'? Which might have elicited such things as 'in restaurants he could never even remember the menu or what he had ordered, in CHX he had to write down where the sailboat was kept because he had such a poor memory' or it might have elicited things like 'I had a general impression that he never forgot an appointment and could recall verbatim late in an evening conversations that had taken place earlier that day'. Anything like this would have clarified matters and advanced the investigation albeit on very tangential issues.