Calling `signOut()` on Firebase Auth with only log you out of Firebase, not Facebook. That's generally how third party auth providers work (e.g. signing out of
console.firebase.google.com with a Google account won't also sign you out of Gmail and Calendar).
If you want to sign a user out of Facebook from your app (not recommended) then you'll need to sign them out using the Facebook SDK instead.
☼, Kato
P.S. If it's not offensive to your culture or beliefs, I'd encourage you to introduce yourself! We are a close-knit family. It's easier to keep that culture strong when we remember that there are real people on the other end of our emails. Getting to know one another by name is a great first step.