While an oversimplification of the truth, it's true within certain restrictions. What information we have suggests that, out-of-world, various members of the dev. team had various impressions of what was under the helm, with none being in-world canon because there was no in-world beneath the helm. It didn't matter and it wasn't going to come up at the time. Out-of-world, it's certainly true that (for some), Nael was always a woman (but perhaps not for everyone).
Yoshida himself has stated (in response to an in-person inquiry by a fan - Rocl, no less) that the now-defined in-world canon is that Nael was always a man in life, regardless of who had what impression when. The female form in-world was an oversight by Bahamut, but out-of-world may have been based on an impression of Nael someone on the dev. team once had. Perhaps even the P himself.
That's not to say that people aren't allowed to form their own interpretations, though.
Nael leaves plenty of room for headcanon and I doubt it's coming up again, lol.