You’re right. It’s the legal precedents / decisions that are the “patients” here. The new cases (that cite those precedents / decisions) are just… let’s say “test results”.
So yes, this is a way to determine causation in relation to what legal precedents / decisions will be cited in new cases depending on the contents of Wikipedia.
I was under the (perhaps mistaken) impression that they claimed a causal link between their Wikipedia articles and the outcome of new cases. The chosen setup cannot IMHO prove such a causal relationship, in the strict statistical sense. That would require randomizing new cases and applying the “treatment” (new Wikipedia articles) only to some of them.
