I've spent my entire career doing this, have been personally "threatened" several times, and until relatively recently kept track of researchers dealing with legal threats. The concern is overblown. In cases that go beyond a nastygram from a lawyer, it is almost always the fact pattern that some aggravating factor is present: a consulting agreement that initiated the testing and forecloses disclosure, or the preservation and/or publication of the PII itself, or attempts to pivot and persist access after finding a vulnerability.

It's an especially superficial argument on this story, where the underlying vulnerability has essentially already been disclosed.