That's why I mentioned the assumption about the velocity distribution. Sure, the velocities aren't Maxwell-Boltzmann, but that doesn't matter too much for getting a sense of the scale of the issue. The way an astrophysicist thinks (I am one) is that if we make generous assumptions and it turns out to not be a problem, then it definitely isn't a problem. Here they have determined it might be a problem, so further study is warranted. It's also a scientist strategy to publish something slightly wrong to encourage more citations.