If an End brand is Hemish, but uses O-U ingridents , really what is the difference?
The other hechsherim don’t accept every OU ingredient and process, only some. The example you gave actually demonstrates the point – if cookies only have an OU, they’re probably not pas Yisroel; with a heimishe hechsher, they are. (I’m not aware of any heimishe hechsher which allows pas palter.)