For something as simple as bean soup Grandma would soak northern beans (small navy beans) until they just begin to sprout then peel them by squeezing them. Both mouth feel and gastro-intestinal benefits cannot be duplicated...
Decades later I understand that by the first signs of sprouting the carbs have changed dramatically and all toxic gasses have been let go. Removing the peel at that point is simply to ensure a better mouth feel...luxury... :)