What consumers expect of a FF-title

[Lucifer]

This is most definitely a spin-off or it would be called ff15. 13-TWO is a spin-off of 13

No.
Final Fantasy 2-14 are not sequels of FF1.
FF8 is not the sequel to FF7. Ok?
Ok.

A spin-off is something in the same universe with no ties to the original cast.
FF13-2 has the same cast with events taking place RIGHT after FF13.

Blame Square for naming all their games, Final Fantasy.
lol