For a moment I thought this was actual co-ax, which would be supremely ironic (it was used in the early days of Ethernet, but twisted pair proved cheaper).
But it looks like neither candidate has a conductive core, although they do have the conductive shell.
The whole point of this technology is to avoid the use of a conductive core, i.e. the use of the TEM propagation mode, in order to avoid the conductive losses caused by electrical currents that pass through the cable.
Instead of that, a propagation mode of the electromagnetic waves based on the reflection of the waves from the walls of the wave guide is used, like in optical fibers, but at much lower frequencies, in order to avoid the conversions between electrical signals and light.
