If someone busts your door open, you still have the option to see whether it's the police swat team (and decide not to fight back because you'd lose by default) or if it's the neighbourhood hooligan gang (you can let your shotgun do the talking because the rest will run when the first goes down). So, while strictly objectively kicking the door in is already initiating, it's not really the first thing that counts - as long as the one coming in doesn't want to kill you no matter what.