Avi K,
I didn’t see that in my edition of the Igros Moshe. Can you point me to the line you are referring to. It seems to me that in Even HaEzer 1:114 he says the opposite.
That being said, my point was that they are not disregarding the idea of dressing modestly, they just have a different definition of what is modest. So they cannot be said to have disregarded the requirement.