|My point was that if we treat XNFj as the image of XNFJ, then we end up with a contradiction, which we wouldn't have if we treated (INFp, ENFj) as the image of (INFJ, ENFJ).)|
Yeah, because you're trying to correlate types between systems by functions. But because the functions are not the same, it doesn't matter the functional contradictions you mention.
INFJ and INFj are the same product. MBTI Ni, Fe and Socionics Ni, Fe are not the same factors. So ENFJ → INFj is both different in product and factor. While ENFj → INFj is different in product, but has the same factors.
That's the most concise way I can put it.
Types are products, functions are factors. MBTI and Socionics disagree with factors, but agree with products.
About "cause and effect", that's not it. I know this sounds arrogant, but approach it as if Socionics is MBTI/JCF done correctly, plus inter-type relations and more.