I'm gonna guess he meant Dagger. That would make it tough, unless you fought a bunch of dragons just before, and you were on top of the chocobo quest (though it doesn't make any difference if you don't take Freya and Amarant), and you have thievery doing 9999 damage anyway.

Yes, according to my theory, If you take Eiko and Vivi but not Steiner, then you will get Steiner as the lead, but if you took the princess, I don't know if the dialogue changes a bit, or the dialogue of acknowledging the princess is skipped. I guess I could check everyone's lvl or something, but that can't be it; Vivi is at a low lvl in my current game (well, 50 compared to like 70).

Does anyone have a file right before you pick your party to go to Oeilvert? Is your list different from mine, if you got Amarant or Dagger? Zidane should say the characters in this order, I think, assuming you could take everyone: "Eiko, Vivi, Steiner, Freya, Quina, Amarant, and Dagger."