Hi @glenf , good question!
It may be that Facebook doesn't force you to use the app instead of the other social media or don't have the correct meta tags to open the correct app (I'm pretty sure they do though, otherwise it's a silly mistake for a great company like that). So they may do that on purpose, it may depend on the browser behaviour or the 'default applications' behaviour/settings.
Personally I'm not using Facebook anymore, maybe one of my collegues can try this out? @James @Jeroen ?
Further, I am wondering if this is an operating system dependent issue; I am testing on android
That may be, you can change the system preferences to open specific urls in specific apps by default. But usually the Facebook app (and others) will change that for you as soon you install the app. It depends per app.
Let me know if this clarifies it a bit 🙂
