A web browser prevents access to permissions like contacts, photos, location. I use Facebook and Instagram very rarely but always do so in a web browser for this very reason. It's not that it's "anonymous" since obviously I'm logged in with my own profile, but it helps to compartmentalize their access both in terms of overall permissions, and the timing of that access. Facebook can't push out an update that sends my location somewhere 24/7 if I don't have a Facebook tab open in my browser.