Ahhhh, those were examples of what is out of balance! I’m so sorry I misunderstood your post.
Each exhibits a situation in which there is no boundary. The first, modesty, is not just about protecting men from sexual temptation or we women would all be wearing space suits year-round. Modesty is more about maintaining one’s own dignity, which includes but is by no means limited to not turning oneself into a advertisement for sex. Going too far in the opposite direction of masking one’s gender altogether would be going too far in the opposite direction for inadequate cause.
Old-time Protestant theology (Calvinism) kind of has behind it a hatred for the physical, which is seen as tainted. And certainly anything from fallen humanity is totally worthless. So women are not only not allowed to be overly sexy, they must be frumpy.
This leads to a denial of the inherent dignity of a woman as a child of God. Her essence, her gender, must be covered up as inherently evil.
I heard a speaker whose name I forget explain the difference between a teetotaller and a person who gives up drinking for God: the teetotaller believes alcohol is evil and so stays away; the giver-upper acknowledges that alcohol is a good, but gives it up for something better (mortification).
Thus the Catholics you met were able to say it’s a question of balance but not able to explain further. There are many areas in which the Church must teach boundaries *on each side *so that we do not give in either to excess or insufficiency. So there is a boundary against looking like an advertisement, and there is a boundart on the opposite side, against looking like one is obliterating what one is. Going too far in the frumpiness direction leads to a rebellion as well.