That's because the new French IR is not an EASA FCL qualification, just as the IMCr isn't. They won't be valid under EASA FCL and will need a conversion deal also. The UK could also pull such an IR out of thin air too, at present, because EASA FCL is still not in force and won't be until next spring with the variations transition periods following.
That was my point, why didn't the CAA just say "the IMCr is staying, don't worry" rather than all this chit chat which has been going around. I am sure the French IR is here to stay...