Sounds reasonable to me, unless you remember the conversation differently?
Civ V as announced: 18 civs.
Civ V as released: 18 civs
Deluxe Edition: +1 civ (and other stuff).
By my math, if they had removed a civ, then the vanilla edition would only have 17.
It's not a matter of what was planned, are adding, or removing. It's more like... Is this gameplay content ready at launch date? Yes? Put it in the base game. End of story.