When the legs are crossed they significantly reduce the ability to act quickly during confrontation (as they would need to be uncrossed first) and when it happens while standing significantly reduces balance. Therefore, leg crossing is an important indicator of the degree of comfort felt in any given situation. When legs are crossed at the ankle people are showing that they see no immediate need to escape.
A person standing in an elevator might stand with their legs crossed, but when a stranger accompanies them, their legs will uncross and their feet will become firmly planted. The subconscious mind is saying to the body that no chances should be taken here. While the fig leaf position says “I’m uncomfortable, but escape is impossible because I must talk with this person” uncrossing the legs says “I have no idea who this person is and am unsure of them” and “I know I can run at anytime, and I will, should the need arise so now it the time to prepare.”