2. What would be medieval would be a superstitious reaction to units of measurement as if they were purity religion cult signifiers rather than simple rational concepts to be converted between at will, depending on the task at hand.
English miles aren't.
Also, the conversion wasn't done correctly, there was no need to convert it al all, and SI units are the preferred unit of measurement in science.
And I think that the press release is in error here. There was no radius measurement proposed in the Nature Astronomy paper. However, the radius in the press release is far to large. See:
https://i.imgur.com/Y34OspJ.png (From https://arxiv.org/pdf/1603.02698.pdf)
Something on the order of 6-10 miles for a 2.14 M neutron star is much more appropriate.
Notice that this measurement may rule out some of our models (mostly the gray lines on the left of the chart) that don't predict neutron stars this massive.
In nautical miles it would be closer to 15 ;-)