Complete silliness. If PJ HAD used his intentional footage of Aragorn sword-fighting with Sauron at the Black Gate, I wonder whom he envisioned winning this fight, and what would have happened after that?
Presumably he intended Aragorn to "win". But if he had won (i.e. killed Sauron with Anduril), would the quest of the ring-bearer immediately become meaningless? If Sauron won, then Aragorn would be dead? A sad beginning for the Fourth Age of Middle Earth.
Neither would have worked, so I imagine PJ probably intended some dramatic stalemate in the fight, or Aragorn in imminent peril of death, but either potentiality resolved just in the nick of time by the Ring+Smeagol falling into the fires of Mount Doom. Or even Aragorn winning heroically and running Sauron through just at the moment the Ring is destroyed (for a complete over-the-top double-kill of Sauron).
At least if Sauron had appeared in physical form to fight at the Black Gate, we might have been spared that scene when the Dark Tower crumbled and the giant eye (which was supposed to actually be Sauron) was furtively looking back and forth in a complete panic as the tower fell. Remember that scene? Sorry if it brings back bad memories...