Yeah, if it's a High Court decision that is exactly what that means. Not that it will go to court - a JR is super, super, super unlikely, to the point of invisibility - but the JR on this exact issue absolutely determines the decisions made on it in lower courts, unless and until a new, equal or higher decision overturns it.
So in this country we have statute, and then also delegated regulations (rules that stem from statute - from Acts of Parliament) which set out the framework, and then judges interpret the law. And yes, previous cases determine the law, moving forward. They are known as legal precedents and they are vital to our system of law. (To complicate things a bit more the government also issue legal guidance, to help interpret statute, but that isn't law and can't amend it nor bind - just has to be given due attention.)
The most junior form of court is a First Tier Tribunal. Those decisions rely on previous caselaw to decide what is correct, but their decisions don't bind any other cases. They're case by case and individually determined. We have them for eg employment disputes, SEND appeals, and benefit appeals. Appeals from them go to the Upper Tribunal, whose decisions DO bind lower Tribunal cases.
Separately, and massively more formally and seriously, you have Judicial Review, which is the nuclear button. Cases go straight to the High Court and are decided by senior judges, and they DO bind everyone else. They decide what is and is not lawful and a JR decision is a massive, massive deal. And that "ONE court case" you refer to was a Judicial Review. That's a big fucking deal and yes, it absolutely binds how the law can be interpreted by everyone else unless and until that's appealed in its own right and goes up even higher (to the Appeal Court, and then after that the only option is the Supreme Court).
That's how our legal system works. The family courts are case-by-case too - so, every decision will turn on its own facts - but also rely on statute and precedents from the higher courts.
The easiest way to describe it is like a massive game of legal Top Trumps.