Ivo, you are, surprisingly, taking the answer too literally.
Besides, Photoshop in itself is not art, but generally requires a lot of technical knowledge. Even today’s photography, cameras in particular, require it.
A lot of composition relies on geometry. Just ask HCB, for instance.
She also said “history and literature.” Someone here recently mentioned a link between poetry and photography.
All of that, general education and accumulated knowledge, from technical to poetic, even if buried in the subconscious, is what makes a person using the massively complex and powerful tool that Photoshop is produce a unique vision with it. Rather than just replicating someone else’s style by knowing which sliders to move first.