• I'm not quite sure what you mean by "pantser," but it conjures up one heck of an image of the writing 'process'
Comes from the expression to drive by the seat of your pants.
But I like the title Misty better, because misties tend to just write, and let the story come at them “from out of the mist.” Heinlein claimed to do that—just put interesting characters with conflicting goals together, and let them take care of the story.
Actually, I suspect that those who practice that approach fall into the category of people who can hold the entire story in their heads, at once, and so can analyze each new development in terms of everything that went before, or is expected in the future. Such people can, without thought, know where to jump back to in order to add or change foreshadowing, as needed. So, they don’t hard-plot simply because they don’t have to.
One disadvantage of being a misty is that it’s easy to write yourself into a corner. The advantage is that if there’s a way out of a dilemma, your character will suggest it to you, making the twists and turns more spontaneous, and interesting.