Actually, I find ExTJ's to be a strange kind of exception to the J rules, or at least in my experience. Naturally I'm talking about how they respond to me and me in return to them, so it could be that it's me that brings out a certain side of them that others don't necessarily see, or vice versa... it's too subjective to be able to tell.
But in general, ExTJ's, and especially ENTJ's, I find tend to be much more flexible with regard to what THEY plan, do, want, etc - than other J types. They don't tend to need plans or schedules for themselves, but what they do instead is to expect others to be scheduled and planned and 'regular as clockwork', they want others to be predictable precisely so that they can freely manoeuvre themselves 'between' others' actions etc.
I'm not sure whether I put that across very well, but I'm trying to say that whilst other J's I've known have tended to acknowledge that others are not able to be predicted all of the time, they want to at least be able to predict, to some extent, their own actions and plans. But ENTJ's are kind of the opposite way round. The main effect of which that I notice, is that they're easier to persuade to change their minds.