I think he was making a distinction between the app and the site. AFAIK, most Facebook users utilize Facebook primarily through the mobile app. If you look at Google trends[0] for Facebook, you'll notice a linear decline since 2011. I believe this is due to the onset of the Facebook mobile app, but feel free to correct me if I'm wrong.
[0] https://trends.google.com/trends/explore?date=all&geo=US&q=f...