Twisted Shielded Core

In the Concentric Twist Layer Design module, the example uses four twisted shielded cables that make up the core. Are both wires in each cable being used, or just the one for a signal? If only one, why was a twisted pair chosen instead of a single shielded wire?

In most cases one is signal, the other is ground, so both are carrying an equal but opposite "signal". This would be common practice for VR sensors or knock sensors which generate an AC waveform.

But even in the case of something like a hall effect sensor it is still common to use 3 core shielded cable even though the power wire doesn't need to be shielded, it is just neater to have all 3 bundled together in a single jacket.