The intermingling argument is actually central to the Bartz settlement structure. The settlement required destruction of the pirated dataset specifically because commingled training data creates an unresolvable provenance problem. For deployers building on Claude, EDPB Opinion 28/2024 requires a documented assessment of the foundation model's training data legal basis before deployment. "We cannot tell which outputs came from which source" is not a satisfactory answer to a regulator running that assessment. wrote about it before here: https://legallayer.substack.com/p/i-read-every-edpb-document...