Alas I cannot give you full passages due to the rules of the Forum. I have paraphrased the important parts and referenced to the material precisely. It does not say what you attributed to it as far as I can see.
I do not understand how the range could be doubled and the distribution reduced unless there is a different mechanism. There are a few clues in the passages despite the clumsy translation.
Certainly the old cannister and grapeshot is explained but not that of the newer construction.
1. The balls of 1.1 and 1.5in diameter had enough momentum to richochet.
2. The cannister was propelled down the gun tube.
3. It is likely that the cannister split when it left the gun tube rather than inside. The clue may well be upon the manner of construction. It was soldered down the seam and upon the lid. The solder was likely to be lead so it is low temperature than the body made of tin.
4. The reasoning for this is that there would be less collisions that reduce the kinetic energy and change the axial direction of the iron balls.
5. There are reports that the cannister did not split even when they struck the ground.
The construction is different from that of British case shot. That seemed to act with the wooden base plate acting as a piston to expell the contents. British case shot had a shorter range than French or was the number of hits upon a target acceptable different.
I think we are closer to its action but the attributed range of French cannister is an anomally when compared to other nations.