They're not. If anything, the fan names are evidence in support of my position. Because it means that fans have identified both of those characters as imposters. fArya is definite, while fAegon is merely suspected of being one at this point. Assuming he is, that gives us a fake Stark and a fake Targaryen in the story, and that makes for a parallel. Do you think it is a coincidence that imposters are being passed off as heirs to the two main houses in the story? If so, what about the fact that these stories take place during the same book? The uncertainty on the Targaryen side of this fArya/fAegon comparison mimics the hidden/secret identities parallel, since in that case there is 100% certainty on the Stark side, but something less than that on the Targaryen side. We know for a fact that the Stark kids are in hiding and using different identities in at least two cases, because it happens during the course of the books. Otoh, we don't know for a fact that Jon Snow, or anyone else, is hidden/secret Targaryen. His identity is presented as a mystery, and RLJ is still technically a theory, regardless of our certainty.
That reminds me of a Stark-Targaryen parallel I mentioned a while back. We, the audience, spend a good deal of time discussing and speculating about (possible) secret/hidden Targaryens; Jon, Tyrion, Aegon, Mel. For us they are something of a mystery. We are not completely sure if any of them actually are blood of the dragon. Largely because the events leading to their secret/hidden status occurred before our story began. Yet, during the course of the story, we see that GRRM has hidden the remaining children from the other main house, the Starks, and given at least Sansa and Arya false identities. Sort of like, for example, "Jon Snow." There's possibly another parallel that has occurred to me, as well. fArya and fAegon. Jeyne Poole being passed off as Arya Stark, and whoever YG really is by birth being passed off as Aegon, son of Rhaegar and Elia.
Does anybody recall the passage where LF tells Sansa something along the lines of, it's impolite to ask a lord about his bastards? I had the feeling that was GRRM's way of partially explaining why Ned wasn't really questioned about Jon's mother.
Exactly. The Smiling Knight made it known that he wanted Dawn. And it's not a coincidence that Tywin did what he did to Ice, while Ned returned Dawn. It's a great way to show just how different the two men were.
No big deal, right? That's a hugely honorable gesture on Ned's part. Not to mention, he delivered the news of Arthur's death. Sure, not happy news, but better than not knowing. So that's a big deal too.
Ashara's suicide was her own choice (if she is in fact dead). Arthur was a knight of the KG who died in battle. Ned was under no obligation to do anything with his body, let alone return Dawn to Starfall.
I recall reading one comment saying that the show might do RLJ as a sort of favor to GRRM.
As to the OP's question, I wouldn't be too terribly upset if it turns out that AD+L=J. I'll be surprised of course. But if I had to pick one alternative to RLJ that I can see working, AD+L=J is my choice. There's enough sword symbolism around Jon to make him work as a Dayne. I don't think it's unreasonable to interpret sword symbolism as meaning Dayne either, since there is a sword on their sigil.
I believe it was a fan correspondence, though I'm not 100% sure. Either way, I don't think it makes much sense to assume he'd choose to answer the question with a lie, rather than just avoid it as he's done probably hundreds of times over the years.