I agree with your points, heck even the classic Macintosh operating system exposed interfaces for end user programmability, but I think the article's author was

I agree with your points, heck even the classic Macintosh operating system exposed interfaces for end user programmability, but I think the article's author was illustrating that this is much closer to the norm for Unix based operating systems. As for piping text around, that is largely a product of a different era. an era when resources were more limited and ideas less developed. Keep in mind that Unix was developed at a time when most interactive systems used glorified typewriters. (While a terminal doesn't have to be a computer, the complexity pretty much necessitates IC's and they quickly evolved into simple computers.)