However, in this day and age, most young women are Niddos, and that in of itself is an ervah (not weighing in on Yichud, which may only be a Takana (depending on Pshat in Avoda Zara 36B)).”
Thank you for the source. I think the problem for me is that we are defining things in a very broad way, that are translated in a more specific way. Thus “erva” conceptually serves to cover the entire gamut of forbidden actions, when the word itself means nudity. In the broader sense, all the posts about it are more understandable.