Doesn’t R’ Moshe give GAW’s logic explicitly in that T’shuvah? That it’s just Lo Yitachen?
I didn’t see it either, although I didn’t read the entire teshuvah.
Besides the fact that you probably imagined that, R’ Moshe’s “lo yitochein” would be based on kol haTorah kulah and nothing else, so it would be a huge bizayon to even use the term OO in the same sentence (which I actually just did…).