Why are there two profile pages in the client, one under achievements and one under friends?

Although similar looking, these two pages are slightly different:  The “Achievements section overview” page is an overview page of all your activity and includes information that is not visible on your profile, but only visible to you. The “Profile overview” page is shown exactly as it would appear to other users. You can change whether to display to “Friends” or to “Everyone” in the top bar. It includes your player picture and bio data as well as your activity feed.