If the View looks like this:

struct Screen: View {
    var body: some View {
        VStack {

            ...

            NavigationLink {
                LoginScreen()
            } label: {
                Text("Sign in")
            }
           .accessibilityIdentifier("TEST_IDENTIFIER")
        }
    }
    .accessibilityRepresentation {
        NavigationLink {
            LoginScreen()
        } label: {
            Text("Sign in")
        }
        .accessibilityIdentifier("TEST_IDENTIFIER_2")
      
        ...

    }
}

and the content of the UITest looks like this:

    let signInButtton = app.buttons["TEST_IDENTIFIER"]
    signInButtton.tap() 

Running some tests shows that the test can only find the signInButton withe the TEST_IDENTIFIER, and when it taps, it taps where the representation of the button would be. Unfortunately the visible button is at a different place. So it taps on a different place of the screen and is not triggering any button presses.

Accessibility wise, it would be useful to have both buttons at a different place, but this way we could not find any way to make the UITest work.