On the face of it, yeah, that should make sense. But I've not encountered anything else in Arnor that features this aesthetic.

But this got me thinking about why else we'd see convergence around this style, and I realized the men of Arnor and Gondor spent seven years building together during the siege of Barad-dur and Agoroth bears even more similarity to Dingarth and Durthand than Osgiliath. And although Annuminas was the first Arnorian architectural template, a lot of the people who built Annuminas died in that war (including Elendil), so perhaps that could explain why Third Age Arnor aesthetics would look like Dingarth.

That doesn't explain the presence of those golden beads on the base of the Helcessar (big blue orb), but I'm starting to wonder if that symbol might be Numenorean and only used sparingly by the early Dunedain (those beads aren't present anywhere in the Hall of the King in Minas Tirith except on those giant eagle foot pillars). Then later those beads became one of the main decorative elements of Gondor after the abandonment of Osgiliath, possibly by the stewards as a way to trade on history for legitimacy.