As shocking as Steven Avery’s case is to Netflix viewers, his wrongful imprisonment for 18 years is not an isolated incident in the troubled US criminal justice system.
In my previous post "As shocking as Steven Avery’s case is to Netflix viewers" I asked question regarding the above sentence. I wrongly thought that the phrase "as…as" indicates the comparative there. I was informed that this phrase in my sentence means the concessive clause. Because I was not able to find this type of the concessive clause anywhere on the internet I was given a link on the article on this matter. There is discussed many types of the concessive clause but the only type which is similar to my exemplary sentence and which uses the pattern with "as" is: Old as he was, he ran fast. Can you explain to me the difference? Why is in the concessive sentence from The Guardian one "as" in addition?