Considering that most people can't read another person at all it is accurate way to describe most people. In fact, it is an expectation that any random person you meet, there is 99% chance that this person falls into that "not so trained eye" category.

Reading people seems to be skill only very few pick up as children and those that do it tends to come from their forced circumstance they happen to find themselves in, like for example: lets say a child settles into a foreign country that doesn't speak their native tongue at all, which leaves no other choice for the child to start to see something that has always been there but has always gone unnoticed - an entirely different communication that doesn't just rely on sound on 85Hz to 255Hz frequency.

Forced situations like that tend to be the usual kick for people that can naturally read other people without any prior rigorous training. Obviously, it is a skill that can be picked up other ways too, so it can obviously be trained too, but again it is one of those unique skillsets that you don't really think one would ever need, so nobody ever bothers with it.

I personally think that it should be a skill that should be picked up just like reading or writing is in education. I think it is equally important and it will change your life if you have that ability.

By the way, I think the lack of that skill in most people is the reason why most movies suck. This is the sole reason why the good and the bad actors tend to show more emotion than it is really necessary for the storytelling purposes. Character in the movies tend to be like idiots that need to say the same thing at least 5 times so even the dumbest individual could understand what is happening.