I can tell you the cable definitely changed with the iPhone 7, as I have owned every iPhone prior. That's when I noticed the cable material texture changed (And others who mentioned this through various threads during the launch of the iPhone 7) when I had my iPhone 7 Plus. Which is when I read something about Apple changing the material (Hence thickness and texture was different) to be more environmentally conscious about the material composition used.
Not what I was referring to at all. That's When it may have started, but That doesn't mean Apple can't change the material to be more environmentally conscious at any given point for 'Cable material', which doesn't have to revolve around the environmentally friendly initiative. I think you're conflating An entirely different topic based of what I stated. Regardless, if you want the most accurate answer to your questions, I would suggest contacting Apple directly who will have more specific information.