No, I am not. Or I wouldn't be able to draw from imagination. Most people get a brief, vague glimpse and act like they can hold an image in their mind.
You aren't holding it if you can't draw from it. End of story.
In my personal case, I can maintain a clear image but be unable to translate it accurately to paper or to another medium (electronic or not) since it involves skill. The fidelity I am able to attain has improved as my skill has improved, and I can clearly see the frustrating differences between the image in my mind and what I then drew without yet being able to remedy it. If the proposition were correct neither of these things would be possible.
You aren't holding it if you can't draw from it. End of story.