From the pattern:

The third of my Wuxing: 5 Elements series of hats is themed for the element of Metal. Each of these hats is pushing the envelope on double-knitting in some way; this one uses a combination of marled garter and textured double-knitting with color-changing cables!

Prepare yourself for a challenge! This hat has the largest variety of techniques of any hat in this collection.

The two layers do not look appreciably different (aside from the cable direction) but there are elements of this hat that could not easily be achieved without the freedom that double-knitting provides.