I never knew that! From their "Integrating Toxicological Assessments in Material Selection for Apple Products" white paper:

"Removal of BFRs and PVC were challenging since alternatives were not readily available at the time. The largest obstacle was identifying a replacement to PVC in AC power cords, where strict safety standards favored PVC and created barriers to its elimination. Apple worked with multiple material suppliers and tested dozens of different formulations until the right combination of performance and safety were achieved with lower toxicological and ecological risk than PVC. Apple then had to persuade dozens of safety agencies around the world to allow it to certify the alternative materials. Millions of PVC-free power cords are in use today with Apple products."

https://www.apple.com/environment/pdf/Toxicology_in_Material...