A small hint surely. :) A hint that he'd been there but not fought there.
No, it was definitely just a hint, but it's obvious, to me at least, that it was there specifically for those Tolkien fans who knew the backstory and could insert exactly what Aragorn was "remembering" in that scene. If you watch Aragorn's face when Boromir is talking about coming home to the sound of silver trumpets, he's not just remembering being at the city, he's remembering just exactly what Boromir is talking about.
However, you're right, it's only a small hint...what is still to come may develop more of that, however. It's a question of whether or not they want to incorporate more of the extra-textual info from the appendices or not, I suppose. I remain very hopeful, though.... ;)