Not saying you’re wrong, but I’m also not sure what could’ve been done to make it more immersive? It sounds like the organ was captured on a stereo pair, which he placed in-between the front and rear speakers. I don’t think it would’ve worked to put it completely in the front or completely in the rear.
Precisely I've been listening to the album today again, and playing special attention to that part. I think it's nicely distributed in the surround field, but to me it has always sounded as if the overall volume of the organ was lower, compared to the other sound elements, than in the original stereo mix. That lessens the impact. I haven't checked levels - it simply has always sounded like that to me, both on my previous and on my current system. I always get the impression that the low end isn't as commading as it could be, too.
Additionally, it wasn't my intention to compare (I did it without thinking about it at all), but I played the Atmos mix of
The Yes Album right afterwards. Then, I noticed something very obvious: the vocal harmonies of
Close to the Edge (5.1) don't sound nearly as good as those of
The Yes Album (Atmos). The former seem kinda disjointed and thin in comparison, forming a triangle around you (from the center channel to the rears). The latter are so much more immersive and coherent, at least to these ears and on my system. It really made me realize how impressive the Atmos mix of
The Yes Album is. I wouldn't change a single thing about it and I consider it to be basically flawless. The 5.1 mix of CTTE, while still very good, really pales in comparison.
I'm confident that SW's Atmos mix of CTTE will correct those "flaws".