When you import an interface there are usually a lot of classes and Jade adds a _1 or greater to the class to make it unique (where there is a class name clash). By having a prefix it allow you to identify it is from that component. There are also other situations where having a prefix would be of benefit.
At the moment you are required to go through each class and specify the prefix taking a long time. It you reimport it then you must go through the same process again resulting in a tedious process. By Providing a simple option to prefix the class (3 chars would be fine but you could allow more), it will save a lot of time and provide greater flexibility for bringing them into Jade.