Talk:The Crystalling - Part 1/@comment-32462018-20180206221513/@comment-4531340-20180207004218

There's a subtle but key distinction there - what they said was it was something Equestria had never seen before (or, to put in more matching terms to yours, it was never recorded in Equestria), not that it's something that never happened.

I mean, in The Journal of the Two Sisters, I believe there's an entire tribe of Alicorns to which Celestia and Luna belong - and it also makes it clear that they were born before the founding of Equestria (so it probably would be accurate that Flurry Heart was the first pony to be born an Alicorn - in Equestria).