It's from the thread on this form regarding Ultimania translations. This is the page on which the info is present, identifiable by the katakana. While there has been debate stirred up based on an incorrect assumption that the XV timeline was actually comments from Tabata, his comments regarding Versus and FNC are from a dedicated page(s) in which he gives this information. There's still loads more interesting-looking information related to FNC to be translated (there's even an incredibly tantalizing little piece about the "Shigai" of XV, and Tabata talks about XIII in his answer so I think it's explaining why they have similar names to Japanese Cie'th or something)
Basically, Tabata states that the story of Versus was built around the "Goddess" (Etro) of the Fabula Nova Crystallis mythology. However when it changed hardware and became a main series entry, the story underwent extensive reassessment. Through this process, the role of the main heroine shifted, and so Stella was replaced with Lunafreya. However, the core plot of Versus was carried over. In addition, the mythos of FNC, which I have already described above", was likewise carried over and incorporated into the world of XV as one of its key elements. He sums up by saying that, despite all the outward changes, the core elements of what was Versus XIII remain intact.
Scan sources:
https://twitter.com/FFplanet/status/814051498405441536
https://twitter.com/FFplanet/status/814051734540599297
Basically, Tabata states that the story of Versus was built around the "Goddess" (Etro) of the Fabula Nova Crystallis mythology. However when it changed hardware and became a main series entry, the story underwent extensive reassessment. Through this process, the role of the main heroine shifted, and so Stella was replaced with Lunafreya. However, the core plot of Versus was carried over. In addition, the mythos of FNC, which I have already described above", was likewise carried over and incorporated into the world of XV as one of its key elements. He sums up by saying that, despite all the outward changes, the core elements of what was Versus XIII remain intact.
Scan sources:
https://twitter.com/FFplanet/status/814051498405441536
https://twitter.com/FFplanet/status/814051734540599297