consider: Sophie isn't the only Moonlark.
Genetics are complicated, hardly understood by elves. The Black Swan's plans are specific and complex - not just anyone will do. Besides, whose first thought is making a child partially out of alicorn DNA?
It takes more than one version of the Moonlark to get it right. the first never make it to life at all, though eventually some do. Perhaps, if this is a dark world, they are killed. Perhaps Calla saves them; perhaps someone insists that they be allowed to live.
The first Moonlarks aren't as stable as Sophie. Their Telepathy is too much for them to handle. Some are left in the Lost Cities, battling what went wrong in their genes, and others make it to the Forbidden Cities before the Black Swan declares them not good enough. These Moonlarks are different, always, grappling with the parts of them they don't understand and never being whisked away to a magical new life. They must realize they're different, someday. And what do they do then? Try and work it out, even when everyone they know grows old as they stay the same as ever and they begin to realize people are getting suspicious.
They never get to figure out what it is. They never find magic. And they never get to warn the last Moonlark of the truth: that they have all just been tools all along.
