The crux of the case is whether Valve is applying that rule to non-Steam keys or not. Lawsuit says they are, Valve says they aren’t. If Valve is telling the truth, they’ve done nothing wrong. If Valve is lying however that is an anticompetitive practice that should be punished. We won’t really know until the trial concludes though.

Personally I think the most likely answer is that some junior support people at Valve misunderstood the policy and told some people the wrong thing. There’s a decent chance that when those accusations first surfaced a decade or so ago (yes this has been a thing for that long) Valve probably sent some internal memos to clarify what the rule actually covers and what it doesn’t and hopefully that was that.