One thought might be - did they

the article mentions "we retrieved only parts of the datasets rather than downloading them in full", so a charitable interpretation might be that for each identified source candidate, they spot checked (or had a model spot check) a few individual records to have incontrovertible proof of breach of privacy, and then ran an aggregate count query to gauge the extent of breach. I think that would be fairly in line with "white hat" behavior that's doing the smallest amount of extra work towards a solid proof and clearly not taking the obvious and easy next step of downloading the remainder that would be required for self enrichment. Difficult to argue that there is an intention of malice.

A bad actor would be downloading /all/ the data and disclosing it to no one, and selling it while obscuring the source.

That said I agree that that certainly might fall afoul of the letter of whatever local laws apply, and certainly prosecutors can also be over-zealous in their interpretations. So personally I would never risk doing something that comes up against that line, from a personal risk POV. But idk if it's fair to argue that this is NOT good faith.