They showed "Stella" a few times briefly a long ass time ago, back when the game was practically... nothing. The team was reshuffled and they began work on the actual game proper. We don't really know if that Stella has been carried over or done away with in favor of a slight redesign and name change, but that's still not a spoiler or anything close to a spoiler. Again, it's a design decision. Characters are frequently redesigned and renamed during production.
If I'm making a movie, and I show concept art for an alien named Teedus, but then I decide I don't like the name "Teedus" and decide to go with "Tidus" instead, that's not a spoiler. It just means that the creator has changed his or her mind, or that something has been altered during production. It sounds like some of you guys are taking "Stella" and creating a myth out of her when it's not that complicated.
And the reason why they don't say stuff about shit sometimes is because they've always been weird about almost everything.