I think that is correct. I've never gotten the impression that my females only contributed size and conformation. And I don't recall hearing of Japanese breeders using females with poor pattern and color just because they had good bodies.
And given the percentage of ginrin young that I have seen relative to the percentage or ginrin oyagoi that I have used, I tend to agree with the theory that whatever gene causes ginrin must be dominant. However, there is some question in my mind on that because you have reported few ginrin in a non-ginrin/ginrin cross. Also I think Sean did the same last year with his yababuki/platinum cross.