I read a while back that for Introverts, the J/P axis isn't clearly differentiated, while for Extroverts, F/T is unclear. So it's common to slip between INTJ and *P.

That and the rest of your post show a clear disposition for Keirsey's definition and not Brigg's.

J/P is not an "axis." It simply explains with of the two shown functions types are extraverted.

Some of the main differences between INTJs and *Ps are that P's tend to disdain social rules as artificial constructs and doesn't think there is any good reason to follow them.

FWIW, the main difference internally, is whether they are dominant Ns (intj) or Ts (intp). And thus, as they develop, are they more like the INFJ (intj) or ISTP (intp). Keirsey only talks about the way they usually interact with the environment, and completely ignore the lifecycle.