With all due respect I think you're making this part up. Nowhere do they ever state anything but Asmita's soul being a shell. The threat from Asmita if the Tenbu Horin landed was because he wanted to test him and see the essence of the 8th sense, and Illias responded with a Lightning Plasma. And Asmita wasn't using the wind as an avatar, it's just that they felt his presence in it (you know, another contradiction to the notion that it's some higher spatial dimension).
Well, sort of. It's true that it's a merely mental plane (Illias even directly states something along the lines this is my territory of thought vs yours), though Illias himself didn't create it. Asmita says this space was a battlefield of their thoughts, and then him and Sisyphos subsequently raised their consciousness to reach it and finally be able to contact Illias.
Illias even states that it was they themselves that reached the mental dimension to contact him, he didn't create it for them. And this is the "higher plane" in question that Asmita says he previously couldn't reach.
But yeah, I definitely agree it's not an actual higher spatial dimension and a new thread to reverse this change is in order. I'll get to it soon.