Seeing through her eyes was useful for the initial stages of the training. It's important to realize that in this story, developing the ability to disappear from sight will be a desirable attribute for a soldier or spy, but the basic purpose behind pushing Ken to work on this capability is to give his expanding and re-organizing brain exercises that will help it develop.
Next up, Ken will learn how to make a coin appear in his hand. Not a magic trick, his skin will exude the materials.
One sees that Ken is being changed in basic and substantial ways, which will make him into a different kind of person.
Here's an implication in regard to this story: If your ship can provide every material need you may require, what will be your purpose in journeying?
... what will be your purpose in journeying?
To get to the other side?
Why do people climb Mt. Everest? It's certainly not because there's anything at the top they need.