KEIRSEY: Why the 'irksome' Asymmetry in Temperament & Interaction Style? Answers given.

I annotated the final graphic shown (interaction style and temperament) which was by Dr Linda Berens and comes from her website bestfittype.com
Why it's the asymmetrical NT, NF, SP, & SJ, rather than the symmetrical NT, NF, SF, ST.

Abstract types (N): temperament is done by NF/NT (Idealist/Rational) and interaction style is done by NJ/NP (directive/informing).
Concrete types (S): temperament is done by SJ/SP (Guardian/Artisan) and interaction style is done by ST/SF (directive/informing).