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It is a good explanation however slightly unclear. This is another explanation:

Case 59/85 Netherlands V Reed – a UK resident went to the Netherlands and applied for a residence permit to be able to live there with her partner, a UK resident working in the Netherlands. The applicants permit was rejected and she applied for a court order to prevent the Dutch authorities from taking action to deport her which was granted to her. But the state appealed. The supreme court of Netherlands asked the ECJ for a preliminary hearing under art 288.

Held, that the right granted by an EEC State to its own nationals to enable them to obtain permission for their non-married partners, who were not nationals of that EEC State, to reside on its territory, was a social advantage within the Council Regulation 1612/68 Art.7(2). Therefore, an EEC State which granted such an advantage to its national workers could not refuse it to workers who were nationals of other EEC States without discriminating on the ground of nationality contrary to the Treaty of Rome 1957 Arts. 7 and 48.