D&D 5E Creative Commons and D&D

[Reynard]

So a big difference between using OGL SRD and CC SRD would be:
1. When writing an OGL supplement you could not reference D&D or the Player's Handbook.
2. When writing a CC supplement you can reference that it is compatible with D&D and you could potentially reference looking something up in the PHB. Maybe even with page numbers? Due to fair use?

Is that correct?

Wasn't there a big case in the 80s over this? What did they decide?