Justin Marshall isn't disputing Jordan's wing form — five tries in two Tests is hard to argue with — but he's making a structural case that the All Blacks are managing a positional compromise rather than solving one. His argument is that Jordan at full-back adds attacking straightness and line-entry quality that McKenzie doesn't replicate, and that the wing choice is essentially a workaround for a thin wing depth chart. The Lomu/Umaga line is a provocation, but the underlying point is serious: the All Blacks are playing Jordan out of position because their alternatives at 14 are limited, not because 15 is accounted for.
The Springbok series is where Marshall sees the real stress test. He flags the Boks' kick-chase unit — Arendse, Kolbe and company — and the highveld conditions as factors that will demand a settled, capable ball-playing full-back. McKenzie has looked fine against France and Italy, but Marshall's concern is that 'fine' won't cut it against a South African side that systematically targets the back three through the air. If you're a Bok supporter, this is a useful read on exactly which All Blacks vulnerability the Springboks may look to exploit across the four-Test series.