Now I'm not an astrophysicist or astronomer but aren't they describing a magnetar, which is a type of neutron star? As far as I know all neutron stars are believed to have a "solid" surface.

Solid in this case is misleading, because this is exotic matter. Neutron stars form when large stars go supernova. The collapse and the gravity are so immense, that the neutrons of the atoms that have made up the parent star actually touch.

This is why a neutron star with a 10km diameter has several masses of the sun.