Because it’s not. You are correct.
We used to call those “fodder beans”. I can recall sitting with my Grandma for hours, stringng fresh string beans on heavy string with big needles. Then we’d hang the strings of strung-up string beans over coat hangers and put them in the windows to dry for several days or a couple of weeks until the pods were brown and leathery-looking.
I’ve never heard “fodder beans”, but Google tells me that’s one of the names they use in east TN/west NC. My granny didn’t string them up; she just spread them out on a big white sheet on the hottest days of the year.