While DNA proves they're the ancestors of all the domestic breeds, to say the ordinary chicken IS a Red Junglefowl, is sort of like saying the domestic dog is a wolf.
I've never owned any Red Junglefowl, and not a lot of people keep them, except maybe in the Hawiian islands, where they're common, or in Asia, where they originated. Maybe you live in an area where a great many people keep Red Junglefowl. I've never seen any around here, that I know of.
What I meant by ordinary chickens, (when I was comparing them to battery chickens) is domestic chickens that people keep at home, rather than commercial battery chickens. I didn't mean the ancestor of all domestic breeds, that hardly anybody actually raises.
I have 4 dogs. A sheep dog, two Lab mixes, and a funny little brown dog that's Bassett hound and who-knows-what. According to prevailing theory, they're all descended from wolves. That's not the same thing as being wolves.