The key information is in this sentences: "We are also pleased to share that we have identified a path forward that balances the legitimate right of all users to privacy and the safety of users on our platform ... while maintaining the ability to prevent and fight abuse on our platform." So they found a balance between privacy and ability to prevent abuse. In other words: this E2E encryption will have some backdoor which will be used only for legal reasons (to prevent abuse, etc.). Just like in the 80's when the US government asked Atari if they can provide encryption for their systems... In was encrypted for everybody, except... the government...