In the Last Samurai, the scene of "Too Many Mind" is explained as to not focus on the people around you, the grass, and so on. But to envision your techniques. Then Tom Cruise slow plays the technique in his mind, which is a great example of what aphantasia can block. It apparently comes in different "levels". Some people can see some shapes, and then different levels of vividness. It also impacts how much people dream. Kinda crazy.