Ni/Ji loops happen, and so do Ne/Te loops. The former occurs when one is extremely introverted and a bit shut off from reality. The latter occurs when one depends too much on external information to for self validation.
In order to be cognitively healthy and mentally productive, however, I'd say that Pi necessitates Je while Pe necessitates Ji.
The labeling system isn't founded on nothing. There is an abstract theory that backs up the labels and the way we've chosen to assign the labels.
Maybe I'm giving Z too much credit, but I don't think he was ever looking for a definitive proof of why Je/Pi-ers should be labeled judgers, and why Pe/Ji-ers should be labeled perceivers. I've only skimmed the thread, but my immediate impression is that he's looking for some kind of conceptual explanation for why Pe/Ji are labeled "perceivers" and why Pi/Je are labeled "judgers." Ie, what conceptual definition does Pi carry with it (if there is one) that can aid in explaining why Pi-ers appear "judgmental" in contrast to Pe-ers, and what conceptual definition does Pe carry with it (if there is one) that can aid in explaining why Pe-ers appear "perceptive" in contrast to Pi-ers.
(I think a better title for this thread would have been "Pi = judger, Ji = perceiver; why?")
Anywho, maybe you could try being contemplative, speculative, and perhaps a bit instructive, rather than criticizing someone for their inquiry before you really even understand the question.