It makes no sense to me to keep filling those gearboxes, designed for 0,9 l with 0,6 l. Its a short time solution and probably pretty soon those boxes will be damaged with wheels spinning around with 12.000 rpm, with less lubrication, less cooling and raising outdoor temperatures. That will be MG's problem, not the owner.
To minimize those huge warranty costs, it makes sense to me that MG has already changed the gearbox, starting with cars with sequential number X or model year 2023?
My guess is model year 2023. G48MG4 has one, build 13 nov, no leak. Of course to be sure you must drain the oil and see how much was in it. Is there a MG4 owner in this forum with model year 2023, with oil leak?