In addition, rating a presentation is a contaminated act. The emphasis is often on excitement. People like to have fun in training courses. Many resent it when the trainer asks them to work hard, even for compelling business reasons. What we need is a clear index of the usefulness of the session, not whether it made people smile.
Surveys tend to focus on what is wrong.
The change-back effect is most likely. The most dramatic effect of training is no effect. Most training does not work. Most intended results are not demonstrably evident. There must be supportive changes in systems that reward and reinforce personal development.