Honestly, I don't.
This is my first post here, but let me explain...
I was sent to Japan as a "youth" (read: 19) in the military. After a couple months, I met someone. Before my 4 year contract was up, we were married and I was already into "adulthood" in Japan.
Under the stricter Japanese immigration laws, I would've needed to become skilled in Japanese in order to become permanent.
However, that was moot at the time because here and there, I'd accept a SOFA job position, subsequently restarting my 10 year clock (had to be on a visa for 10 years to be considered).
I can't recall when the immigration laws changed, but between the strict policy and the loosening of it, I obtained a bachelors, and then an MBA through a US school.
Those two, held weight when I applied for permanent after the loosening.
While JLPT might get you a point closer, I want to say that they took a look at my personal background and I became the first permanent resident without JLPT (having someone else write in kanji why I want it) in 2 months, which is 2 months quicker than average—without a "gift", if you get my drift (as if Japan is corrupt).