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.
That doesn't sound plausible.
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.