Why Exchanging Data With Facebook Is Problematic?
As mentioned in the new policy, WhatsApp is likely to use your data is to provide better service, improve user experience & make sure better security for the user by brawling spam.
However, if you use WhatsApp services with third-party services or with Facebook Company Products, they may obtain your information. For example, if you use the WhatsApp share button for sharing any news/product listed on an e-commerce website or if you access the services/share content with WhatsApp business accounts; your content is likely to be shared with Facebook and third-party service providers.
So, don't bewilder when you can see products/services similar to what you have been seeing or asking from your friends & family.