All I can say right now, is Thanks for the warning!
I will be even more selective of when I do or do not answer my door.
In my present apartment complex, it’s not that uncommon to get a knock on the door. Maybe somebody’s Soccer Ball was kicked into my fenced area. Maybe someone received an Amazon package addressed to me, etc. Let’s just say, if I ignore such knocks for now, it won’t necessarily be the Apocalypse.
I also only answer/open my door for delivery people/known neighbors. And even though my front door is glass, I have absolutely no problem pretending that you are not there, and I am invisible.