That's about right. The intent behind the informal description is to provide additional information about the entity and fact types. There are schools of thought that place a heavy emphasis on informal descriptions and links/hierarchies between such descriptions. However, I've never been able to write more that a few informal description lines without overlapping the formal portions of the model, so I rarely spend much time in exhaustive informal descriptions except as a way to extra formal model information.
The only other difference is that NORMA has an option to display informal descriptions in tooltips on the model, whereas the notes appear only in verbalizations.
In any case, NORMA doesn't do anything beyond verbalization with either of these informal fields, so it is up to the user where they want to place the data.