French powders S, J, and M are all various forms of semi-smokeless powder, that do not measure the same (equivalent) for proof, or cartridge loadings. They differ in this respect with black powder, as well. Powder T is a true, progressive, smokeless powder, and came into use for French proof in 1900.
You can still specify proof with a powder other than smokeless T in France. That said, you can still get a 24, or 32 gauge there, as well.
Neither event is to be considered common, or, normal.
Best,
Ted