From the actual study and the universities own videos, it’s more that they figured out a way to shape a custom lattice based on the shape of the object. This ugly brain man shows the idea off more than the clean looking prints in OP’s article.
BCOVertigo
NatureFree-form thermal cloaks in three dimensions - Nature CommunicationsPhysical realization of 3D omnidirectional thermal cloaking of arbitrarily objects with record-breaking complexity by integrating of 3D graded lattice microstructure, a 3D de homogenization technique, and additive manufacturing.