The judge may have said it can be used in this one case, but unless struck down by another court, it sets up a precedent for other judges to do the same.
IANAL, so I can't say for sure, but it's unlikely. The magistrate didn't rule on a matter of law, only on a matter of procedure (i.e. how to serve a notice). Judges in most cases are typically free to set procedural changes if necessary at their discretion, no precedent required. It's not a formal court decision, it's a discretionary alteration to formal procedure made necessary by the difficulty in contacting the ex-wife. And of course it's a low level judge anyways: their decisions of any kind tend to carry very little weight with other courts.
Of course, other judges who hear about the case may decide on their own judgment to do likewise, but there is nothing legally obligating or even inclining them to do so.