From what I fouind - the webview is used in facebook messenger and links for the timeline and other webview items are from the facebook built in browser - not the whole app itself. i wont be using an in app browser. i have created a facebook clone already using no webviews. but again - it is a learniing experience and keeps certain clientelle happy that I am at least looking into it. I have tried on many occasions to convince not to use an app - but some people are particular. and if i dont do it - they will pay someone else to.
Take facebook for example. You can view facebook in your browser and it is not much different than the app - but the app is just so much easier to use.
I am finding tons of information all over the web that indicates that the facebooks app does indeed use webviews. This is just one of dozens of links i have found. https://blog.tomayac.com/2019/12/09/inspecting-facebooks-webview/
Then there is this link https://www.uxmatters.com/mt/archives/2018/08/mobile-apps-native-hybrid-and-webviews.php which is indicating that Facebook, Evernote, Instagram, LinkedIn, Uber, Slack, Twitter, Gmail, the Amazon Appstore all use webviews.
However you choose to do it, best of luck. I hope you succeed.