The way I understood the patch notes is, that you can exchange the actual pendants NOT pendants that have already been attached to a hair accessory.
I will confirm/debunk this as soon as I am able to get in. I have a dex pendant waiting that I never attached to a hair accessory.
With this change, head accessory pendants obtained before Glory Days can be exchanged for new pendants via the Aden Reconstruction NPCs, Eeny in Talking Island Village and Moe in Giran.