Interesting, if true. But they did have G Gundam stuff, they just had it in a way that didn't reveal any plot points.
Like Master Asia was a good guy like he seems in the first episodes of the Shinjuku Arc, and Kioji was pilot of the final form of Dark Gundam instead of Rain.
They could have at least left in Zeta Gundam itself, like they did with ZZ. But it doesn't matter now of course.