Attacker wants Victim's code. Attacker calls the Bank impersonating Victim, and also calls Victim impersonating the Bank. Bank tells Attacker the code check, Attacker tells Victim the code check, Victim sees the match and enters their PIN into the Smart-ID app, and Attacker's phone session with Bank is now fully authenticated and has no more need for Victim.
Attacker wants Victim's code. Attacker calls the Bank impersonating Victim, and also calls Victim impersonating the Bank. Bank tells Attacker the code check, Attacker tells Victim the code check, Victim sees the match and enters their PIN into the Smart-ID app, and Attacker's phone session with Bank is now fully authenticated and has no more need for Victim.