During Tony's orientation to select his future occupation, he seems surprised that he's been chosen to be an artist. However, later in the film when he visits his "widow" we find out that he's been painting watercolors for many years. Opinions?
There is no "off" position on the genius switch.
I suppose Tony seemed startled at being assigned the identity of a successful artist because as Arthur he might have doubted he had any real talent, considering himself a mere dauber in his spare time.
It's interesting though as Tony seems unable to progress or feel satisfied with any of his paintings, but Arthur had at least a collection of finished works.