From the study's FAQ[0]: > Did an Institutional Review Board consider this study? > We submitted an application detailing our research methods to the Princeton University Institutional Review Board, which determined that our study does not constitute human subjects research. From the social experiment[as reported by OP's link]: > I look forward to your reply without undue delay and at most within 45 days of this emai…
I don’t think it’s intended as a veiled threat of a lawsuit so much as a statement of the compliance requirements. Unfortunately it seems they misunderstood the scope which makes the it inaccurate. But if the statement was true and accurate I would just take it as a helpful reminder of the timeframe.
It's either a veiled threat or a serious error. Either way, this study needed more oversight.