One of the primary reasons to update these documents is also to make clear that they have rolled out end-to-end encryption. The users got notified of it on all individual and group chats, weeks ago, when the latest update was rolled out. When the users are using the latest version of WhatsApp, the messages are encrypted by default. This essentially means the user is the only person who can read them. The changes include emphasis on the fact that the app won’t post or share phone numbers with others, including on Facebook, or sell them to advertisers.
However, coordinating with Facebook will help them to do things like track basic stats about how often people use the services and fight spam on WhatsApp. By connecting the phone number with Facebook’s systems, Facebook offers better friend suggestions and shows more relevant ads if the user has an account with them. For example, users will get advertisements from companies posting about jobs relevant to their stream.
The end to end encryption system is supposed to be a rock solid protection in terms of privacy. However, users have often complained about getting Facebook advertisements about the things that they recently talked about with someone on WhatsApp.