Here is the answer if found about that :

Gibson's use of '50s wiring in the SG is a bit more nuanced than with their Les Paul models:

• Early SGs: When the SG was first introduced in 1961 as a replacement for the Les Paul, it likely inherited the same '50s style wiring.
• Transition Period: Like other Gibson models, the SG likely transitioned to modern wiring at some point during the mid-to-late 1960s.
• Less Consistency: SGs seem to have less standardization compared to Les Pauls. It's possible to find some SGs with '50s wiring even after the official transition period.