Mike, I have heard and read the same thing over the years. First, the .32 ACP won't feed. In fact, it .32 ACP of three makes won't even fit into the magazine of my 35S; they will fit into the 35A magazine.
Then they won't feed; the rims will fit in the breech face, but in feeding hang up on the extractors. If they did, they would be supported on the extractors, since they would not headspace properly.
But that doesn't really matter. The French guns are locked breech, recoil operated, and the factory .32 ACP with its light bullet and relatively low charge just doesn't have enough oomph to work them reliably. The French cartridge case is longer, has a longer and heavier (85 grain) bullet, and a heavier powder charge.
Could the .32 ACP and the guns be modified to work? I think so, if one wanted to spend the time and effort.
P.S. It is often written that the French 7.65 Longue is the same as the Pedersen device cartridge. That is not true. The cases are the same, but the French round, with its longer bullet, won't fit in the Pedersen device magazine. The usual story is that the U.S. left millions of rounds of Cartridge, Pistol, Ball, Caliber .30, M1918 in France and the thrifty French made pistols to use it. I have no doubt that the Pedersen device round was the starting point for the 7.65 Longue, but the cartridges are not identical.
Jim