Low migration rate in Papadopoulou et al. (2008)
After a quick look-up, they don't seem to comment much on this choice of parameter unfortunately. Here are my quick thoughts.

They are dealing with quasi isolated species. They explored a range of values and I would like to assume that made sure that more extreme values won't yield to drastically different results.

These simulations can be pretty computationally intensive, it is possible that they considered $Nm$ to be the important statistic but they would assume that the results could scale up and down for different $N$ and $m$ values. In fact, they almost systematically refer to their migration rate as $Nm$.