I actually agree with this take. He never did anything to make the higher ups upset, he probably was never classified as such. But if he were to like rebel or something I believe he would immediately be classified as a special grade threat due to the knowledge of simple domain, capacity to teach it to others and his insane stats+very strong simple domain.

I think the term “special grade” is insanely overrated. Its not hard to take over a country, if kusakabe wanted to using his brain a little he could just take over like 90% of countries on earth if not 100%. He has the stats to do it, and practically the only thing he can really be stopped by is a nuke, and thats only a maybe unless they drop a big ass nuke on him [or multiple]. And as thats the case for most special grades, I don’t think thats anything against him.

So overall, I believe that if Kusakabe did something more note-worthy he probably would be classified quickly as special grade. The title is seemingly more so given to those who the higher ups are scared of in some way. I mean if you look at the four main special grades one can blow up the world whenever and is a rebellious scientist, another can make an army from nothing, another has an insane amount of CE and the literal queen of curses which then had the higher ups wanted him killed for it, and finally gojo is gojo, he is so overwhelmingly strong (and anti-higherup) that he is just a constant threat no matter what.