Why specifically Soft Point? I've read on a few occasions that ANY non-corrosive rounds shot after corrosive would "clean" the bore. The recommended number of non-corrosive shots would vary from 5 to 10. Personally, I take it with a grain of salt.
Because it's the only definitely not corrosive ammo I have for that caliber. And the only 2 shots is because I am cheap. I always deep clean my Russian guns withing 48 hours of shooting