Do Composite Fillings Need to Be Removed for Gum Graft?

My periodontist said that gingiva doesn't attach to composite filling on teeth. It only attached to cementum. So he has to remove my composite filling to correct my receding gum. I can't find out if this is accurate that dental gingiva doesn't attach to composite filling. I'm concerned that once the gum graft is performed the gums being pulled lower to fix the recession and tooth sensitivity will make it difficult to have the composite filling restored.