He does explain the 9th sense in GA, Aiolia explains in mid fight with Ikki. And the first thing Aiolos does with the 9th sense is void manipulation. I genuinely think you just don’t read the manga or you’re reading very poor translations.
And the 8th sense is not the ultimate sense in classic, it has and always will be the Divine Will. Which, I kind of think it’s funny how you mention Shura has lost his sense of self in the form of his personality being destroyed, you could say once he gets a “will” of his own in this state he’ll be able to start imposing it on others, just like the gods in classic do with their divine will.
honestly, if Okada sets up the absolute divine consciousness to be the first step to awakening the divine will, it would make perfect sense with what the senses represent as a whole.
the first 8 senses involve evolving yourself as a human, becoming an enlightened being capable of controlling your mortal soul. The 9th sense requires you abandon your humanity and embrace nothingness which then allows you to transcend your humanity, immortalising your soul and becoming a god.
honestly, this sounds like something Kurumada planned out when writing classic.
That's not an explanation, because Okada doesn't even bother to explain what the void power of the 9th Sense is, it's just presented as a generic power up with power greater than an Athena Exclamation (with the pathetic description of this manga). A pathetic power for a God Saint in the original manga.
The concept of divine will is never mentioned that way in the original manga, the divine will is not a level or some nonsense like that, gods are powerful because they are gods and they are born as gods, they don't awaken anything to gain their power. The concept of the senses was always limited to humans, and Athena because she is a goddess reincarnates as a human, and for Kurumada the maximum sense is the 8th Sense, the sense that allows the Saints to transcend death and human limitations, reaching a new level of existence that not even the gods can reach.
The gods do not awaken any divine will, this was never mentioned in the manga, and was only mentioned in the Hypermyth, a work that never had any importance for Kurumada's manga. In the manga even Shaka had to reveal the secret of the 8th Sense to Athena so that she could awaken that sense. The 8th Sense is a power that not even the gods possess, even Asclepius who probably fully masters this sense has powers that Athena does not have, for example he can resurrect the dead from the Underworld and see the future, past and present, something similar to the Gold Saints now exist in a completely different plane of existence, even after destroying their body and soul, and can move freely through space and time.
Kurumada didn't plan any of this, and he doesn't even mention it in his manga, nor does he mention it in any of his interviews about the future of the series. This is clearly a nonsense that Okada invented.
Did you miss the part where Shura is only a Saint in title only? He’s literally stayed to transcend humanity bro, how can you say all that bs and act like it applies to Shura atm?
Shura is still wearing a Gold Cloth, an armor that did not transform into a God Cloth even though it has the blood of Athena.