The prof overseeing the paper clarified that they initially did not seek IRB approval, and then received an IRB exemption [0]. I'd want to ask the IRB why they approved that, for starters. Maybe because they'd already done the research and hoped it would blow over, vs. the controversy of rejecting it when they'd already done the work?

0: https://www-users.cs.umn.edu/~kjlu/papers/clarifications-hc....