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I don't know where you get the impression that I, or anyone else for that matter, would claim that UZR is the end of the discussion. Nor that UZR proponents ever claim that their metric does anything to capture park factors beyond simply accounting for the average rate at which base hits fall in each park/sector.
My claim is that there are very specific TYPES of players that benefit more or less from a park's impact on defense and that the primary explanation is defensive alignments that suit a particular player's strengths or weaknesses. Defense is a team sport and no single-player metric like UZR is ever going to capture that.