It's not true, at least not in the sense that's implied. If you read the study you'll see they defined "idle load" not as electronics but as all devices which operate passively.

They did ten case studies, and in one they found the highest idle load device was a water recirculation pump and the second was a halogen light being left on 24/7 because no one cared.

If they studied my home they would consider my fish tanks as "idle load," because they are designed to run continuously.

This is not a study of devices in sleep mode. This is a study primarily measuring devices left on, or devices designed to always be on.