Rather like the nutrition facts label on food packages, the short notice on apps is intended to which reveal at a glance how much of what you don’t want in your diet is in it. Also like the packaged food industry, the voluntary code frees companies from a mandatory label that might rate its data collection policies according to a government standard.
There's a parallel to the nutrition labels printed on packaged food. If there were a legal mandate, then all apps could have a point rating to reflect how privacy-friendly (or not) they are. But without that, it's up to companies to be self-regulating, as it were, and voluntarily decide to briefly show some of its data collection facts.
This week's Advertising Age includes http://adage.com/article/news/big-food-preps-50m-push-facts-front-labeling/243475/. The food manufacturer want to avoid having a legal mandate, so they are spending $50 million to promote what they call ad "Facts Up Front." The idea is that putting that nutrional summation on the front of the package will satisfy those who are critical of the way they have represented sugary cereals and such as sound nutritional choices without having to accept an offical label that is not within their own control like the grade system recommended by the Institute of Medicine. With such a label, the foods that contain more fat, sodium, or sugar than the benchmarks set for them would get no stars at all.