[MBTI General] Question about the type's group pairings

[Megatron]

Hi, everyone.

I'm relatively new to MBTI and I have a question in regards to the four groupings of the types (Idyllic, Arthouse, Guardhouse, and Rationale).

Idyllic and Rationale are grouped together based off of their two middle letters (NF or NT).

While Art and Guard houses are grouped based off of their second and last letters (SP or SJ)

My question is why are the S's and the N's not grouped the same? In other words, why are the functions paired the way they are to form these four categories?

Examples of alternative groupings: NF, NT, SF, & ST or NP, NJ, SP, & SJ.

I'm certain there is a wonderful explanation to this; I just can't seem to figure out what the explanation is. Or perhaps I am just too lazy to figure it out myself. Whichever lol

If anyone could give some insight to this or direct me to a link that can explain it, I would greatly appreciate it

 

[reckful]

See this post.

 

[Megatron]

See this post.

Thank you!

 

[Yama]

I prefer it to go off the irrational axis. So SJ SP NJ NP.