A decision absolutely is precedence before it's been challenged. Otherwise, there's be nothing to challenge - a challenge is an attempt to change the existing precedence and create a new status quo on something.
You are mistaken. Say a lower court delivers a ruling. That is not precedent, but it is the Law of the Land until overturned. Say an appeals court upholds that ruling... then the ruling becomes precedent. If never challenged, it isn't precedent, merely the law. Roe was the law of the land but didn't establish precedence until upheld in Casey. If precedent occurred on the initial ruling, that ruling could never be challenged as courts are compelled to uphold precedent of previous rulings until such time as challenges reach a higher court and are overturned.
Roe was law, certainly, but only after Casey were courts compelled to treat it as established precedent as the findings in Roe were reasserted. Prior to Casey, Roe had not been seriously challenged in a way that would affect Roe. Casey upheld Roe, establishing Roe as precedent. If today, the Supreme Court issued a finding overturning Roe, it would be law, but that would not establish any precedent. It would be ignoring precedent. But subsequently if this new ruling overturning Roe was challenged and upheld, only then does it become precedent.
Not every finding of the Supreme Count or any court establishes precedent. Only the findings upholding previous cases allow those previous cases to become precedent. Otherwise, the word "precedent" becomes superfluous and has no distinct meaning from "the law."
