As I understand it, the hachiriki are not common in other forms of Shinto. If the hachiriki of Omoto do correspond to Chinese trigrams then I wonder if new light might be shed on Osensei's trips to Manchuria with Deguchi. I also wonder if the hachiriki crop up in any of Takeda's training.
It may - but my hunch is that the methodology was already in place by the time those trips occurred. Note that Kiichi Hogen (from the 1100's) was familiar with that cosmology - so there's no need to go back to pre-war China as a source for the information.