This was a show with no grasp of time, no grasp of distance, and no grasp of even fantasy realism - swimming from Valinor back to Middle Earth? Shrugging off a pyroclastic flow? - so I'm not surprised it has no grasp of Hero Props.
"Hero Prop" is the term for Boromir's armour, indeed any armour, costume or accoutrements worn by a Principal Character in LOTR or any other movie.
"Hero" has nothing to do with the character's alignment, applying to Sauron and the Witch-King as well. It means any costume, weapon etc. made as detailed as possible because the character wearing it will be front and centre in very close shots, where an IMAX screen might make any flaws a metre high.
(Bernard Hill was amazed by the details in Théoden's armour, some of which only he and his dresser ever saw. More here.)
Now there's the Numenorean bargain-basement rig up there, and the full plate of the Action Heroine here.
I don't know what it's made of, but it looks like vac-formed, spray-painted plastic.
Compare it to an example of Elven armour from The Hobbit movies, which notoriously didn't have anything like the development time of LOTR...
No further comment.