The main point of the teshuvos is that the point of a mechitzah is to show a separation between men and women, not to hide the women.
Wrong. It must be at least 66 inches according to Rav Moshe. The women must in fact NOT be visible to the men. If it isn’t high enough, the shul is treif.
I once asked a Charedi rav about a mechitza and he said the minimum is 36 inches, so 4 feet is OK.
No Orthodox Rov, let alone a Chareidi one, ever said that.