INFJ doorslams can seem like the purest expression of not wanting to talk with someone in the world. I mean, I know it's happened to me, and it's difficult to figure out when I don't know where I stand with the INFJ. I know Peguy mentioned being it basically being the consequence of being overwhelmed and absorbing too much undesirable energy from someone, which I can understand, especially if the INFJ is trying to reevaluate where the best use of their time would be. I've even doorslammed people, but in my case it's more like nobody's home in the first place. Once you put the foot in my door, it's hard to get you out of my system, which means that I have to be vigilant about who romps around in my inner-life in the first place. I guess my point is that, in my experience, INFJ doorslams can be utterly unpredictable and mysterious in how they were caused, depending on the INFJ. INFJs can be pretty mild but it seems like their paths in life, and how their paths converge with the paths of others, can change radically and subtly. The discreteness can make it seem even more radical and bewildering.
It's not up to me how anyone else lives their life, but if I were to doorslam someone, I would make it clear that I was going to doorslam them. Yeah, explanations can dissolve the significance of the act itself. Nobody needs to know "Why" you do anything, and rationalizing it to someone else only makes you more vulnerable to scrutiny, putting an INFJ in a difficult situation if they are sympathetically invested in an individual they want to divorce themselves from. But vanishing off the face of the Earth's crust without sending a memo doesn't seem quite appropriate imo.