Overseas student loan threshold

IS1965

Hi, my son is on Plan 2 and currently lives and works in France. Despite earning only approximately £23.5k and being below the current threshold for France of £27,295 he has received a letter from SLC stating that for 2024-5 he will be paying £34 P/m. Although not a big sum he has queried this with SLC who told him that the overseas threshold is being reduced to £21k for the coming year for him thereby putting him 'in play' to make repayments. He was told that no formal announcement had been made as yet and having researched I can not find anything that confirms this or otherwise. Has anyone received similar letters or have any knowledge of this at all please? 
Thanks