Social security co-ordination rules in Réunion

Réunion is one of the French overseas departments where EU law, subject to some derogations, applies in full: article 355 TFEU. Our French national client wants to return to the island and wants to know whether he will keep his retirement pension (not yet sure what category) and if it will continue to be up-rated.

Does anyone know if there are any derogations as regards Regulation 883/2004 and the exportability of retirement pensions to Réunion? I can’t immiediately see anything in the Regulation itself.