I thought that maybe we do not see ourselves, but the Dragonborn impersonating us with a Disguise Self spell. I think that the prophecy maybe warns us that Julikar Caeziryn could commit the next crime disguised as Tav, so that we will be blamed for it.
Ooh, interesting!
Now I’m totally getting carried away. Could Grom Skullsmash actually be a dragonborn using Disguise Self? The limitations of the spell might help explain the hulking size unusual for a Githyanki.
"You may call it 'nonsense' if you like, but I've heard nonsense, compared with which that would be as sensible as a dictionary!"