It's from 16p theory. Though that is based on dichotomies, and most people interpret MBTI with cognitive functions.Not related to MBTI at all, this is a factor of the big five neuroticism scale, yes there are many INFJs(or whatever type) who are low in this scale. INFJ would just correlate to someone who is high in openness(N), high in conscientiousness(J), low in extroversion(I), and higher in agreeableness(F).
There is scale called assertive vs turbulent that somewhat takes neuroticism(and traits of conscientiousness) into account.
I don't agree with this, in fact ExxPs can sometimes be very volatile and irritable, I'm thinking of my ENFP sister who is very "touchy" and has "bad nerves" by her own admission. Trust me she does not wait until a tidal wave reaches her to react.IxxJ types will stress all the time but usually over nothing. Meanwhile ExxP types are the most careless and free of all until a tidal wave catches up to them, at which point stress will go through the roof and become unbearable.
Then IxxP and ExxJ types are somewhere in the middle of that spectrum.