Hi Tunneler
Not quite. Some years after the War was over, at the request of families, special memorial diplomas were nominally available which carried the mention that MM + Croix de guerre were awarded posthumusly.
Families who cared about this would often buy the awards (as is usually the case for most french awards) and had them framed with the diploma.
It was the same idea as the british death-plaque. It reflected the way the French felt the dead should be honored.
A bit confusing possibly, but the French understood all this. I don't know if the same was established for WW2, but I rather doubt it.
Regards
Vétéran