How do I create a button that resets the authentication status in SwiftUI?

Question

In my app I have a login page where registered users can either type their pin code or use Touch/Face ID to unlock the app. I have this code for the authentication:

class AuthenticationManager {
    
    let context = LAContext()
    var error: NSError?
    
    func authenticate(closure: @escaping(_ : Bool)->()) {
        if context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) {
            let reason = "Authentication through Face/Touch ID"
            context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: reason) { success, authenticationError in
                if success {
                    closure(true)
                } else {
                    closure(false)
                }
            }
        } else {
            closure(false)
        }
    }
    
    func lockDevice() {
        context.invalidate()
    }
    
}

I was trying to add a button as a navigation bar item that allowed the user to lock the app and get back to the login page where he/she has to insert the pin code to access their data (or authenticate again with Touch/Face ID), like this:

struct ContentView : View {
    
    @State var authenticated = false
    let am = AuthenticationManager()
    
    var body : some View {
        NavigationView {
            VStack {
                if authenticated {
                    HomePage()
                } else {
                    Login()
                        .onAppear {
                            am.authenticate { value in
                                authenticated = value
                            }
                        }
                }
            }
            .navigationBarItems(trailing:
                                    Button {
                                        withAnimation {
                                            authenticated = false 
                                             am.lockDevice()
                                               }
                                            } label: {
                                            Image(systemName: "lock.open")
                                               .foregroundColor(.yellow)
                                               .padding()
                                             }
            )
        }
    }
    
}

However, the lockDevice() function as I wrote it completely blocks the usage of biometric authentication, while I wanted to lock the app. I tried to simply put the authenticated bool on false: it show the Login page, but it's as if you're already authenticated. I tried covering the camera, but instead of the message "Face not authenticated" (which would indicate that the device had actually re-locked the biometric authentication) you get authenticated without any kind of face/finger check. How can I fix this?