Fortunately this skill can be learned by most of us for whom this is unintuitive. I have had to actively learn about body language cues for all sorts of situations. I can now do it reasonably well, but I have to pay attention a bit and do it consciously. Some people can't learn this, but they are pretty rare, and it is pretty obvious that they have problems with it, and as such, a wider leeway is given by most people out of compassion.