From the article's final paragraph: "Apple does more than anyone else to protect user privacy, but this is an area where it’s impossible for users to get any kind of steer on what’s really going on under the hood. We either need Apple to do more, or for the law to do so."
"First, while there is much breathless reporting of data being sent to companies like Google and Facebook, the vast majority of it is innocuous. It’s simply developers using app analytics services provided by these companies, and they are learning things like which app features people do and don’t use.Washington Post finds 5,400 app trackers sending data from an iPhone | 9to5Mac
Second, the Privacy Pro app that The Washington Post was using to monitor the tracker traffic was provided by a company that would like to sell you in-app purchases to block this traffic, so the company concerned has a vested interest in making the situation sound scarier than it is."