And in at least two of those cases, it wasn't intentional, as in "We'll show those running dog capitalists! We'll make guns that can't use their ammo, but which can use our ammo!"
It was done for well-considered and somewhat practical design reasons.
Oh, and just so as you know, the Soviets, once they ran out of ammo that they had purchased with the C96 Mausers in the 1920s, issued Tokarev ammo to those individuals who were armed with a Broomhandle.
The reason why?
Balistics of the original Soviet 7.62 round were not all that much different from the ballistics of the 7.63 Mauser round.
The markedly higher velocities that you see, which everyone thinks means a super high pressure cartridge?
Those velocity readings are achieved through the longer barrels of the PPD, the PPSh, and PPS submachine guns...
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.