Arthur's Balck Lung

Did y'all notice that Arthur's cough starts showing up in Chapter 4?

I was doing one of Strauss's missions and Arthur starts coughing though it's not nearly as bad as it is in Chapters 5 and 6. I've looked it up though and everyone says the coughing is exclusive to Chapters 5 and 6. I cant recall more times thag he coughs but it was definitely in that mission. I do remember him coughing and me cringing multiple times throughout chapter 5 though. Has anyone else noticed that?