I'm not sure I agree with salted beans not softening a myth. I've had problems if I add salt to beans while cooking. Maybe it depends on the bean, I don't know.

The salt in the pressure cooked version seems to keep the beans together, but it's only used during the soaking stage, and the beans are thoroughly washed before cooking . Pressure cooking soaked beans sometimes turns them to mush. This seems to prevent that. Cooking time and of course the type of bean you're using also has an effect.

The Ro-Tel tomatoes used in the recipe I posted don't seem to have a hardening effect on the beans. Probably because they don't cook but for 20 minutes.