Yep that is what I mean. Are your weights/deformations attached to the single IK chain. In the reference its looks like some of the weighting for the single IK (clavicle/shoulder) has influences on the shoulder, the clavicle, some of the pectoral region and down the back along the Latissimus Dorsi and a bit of the Serratus Anterior. It looks like a lot of weighting is shared in those regions. It appears to be a combination between Joint setup and skinning/deformation regions.
The deformations are definitely more organic because of the distribution of weighting by what would be muscles regions on typical human anatomy.