There is a difference between what actually happens and your interpretation about those events. It is natural and normal for people to observe events and then make inferences, interpretations, judgments, and evaluations about them.
However, many people confuse their interpretations with the facts of the situation. In the L.E.T., Conflict Resolution Workshop or Synergistic Selling workshop you took, you were most likely coached to begin conversations with the facts - especially when there are problems. The trouble with GLOP's is that they always include some guesswork about the other person's intentions or motives - something that exists only within the other person's head. As skillful as we may be in our interpretation of another person's behavior, we simply do not know for certain what causes another person to behave in the way they do.
One danger of this is that we will stay stuck in our interpretations and fail to see more effective ways of communicating. Although, we cannot change past events, we are free to choose how we perceive and interpret events.
Perceptions are subject to influence by everything that we have experienced in our lives - where we were born, where we went to school, what our parents were like, our religion, education, - and tend to create a bias and a particular point of view about the actions of others.
Throughout the workshop you took, you were coached to distinguish between what you actually see the other person do or hear them say and how you interpret those actions. This does not mean that your interpretations are wrong or right. It's just more effective to begin such communication with the facts - what we have actually observed. Here is some additional information about GLOPs: