Yeah, one of the quirks of ponycollecting - date on hoof doesn't mean date of release. It's the date the pose was first used, and in the case of that one it would've been 1984, for Baby Ember. Any pony using that pose afterwards has the same date stamp, as it's the date of the pose being created I guess.
Wiki is wrong about some things, but this isn't one of them
I think I'm right that her name isn't officially 'Baby Stockings', that was a fan name coined for her because of her symbol and the fact an adult Stockings exist. I mention this because I wonder if that was why you were curious if she had an earlier date, since the adult was out a lot earlier on.
I think she's just known as the Rice Krispies baby otherwise.