Multiplying two 100 digit numbers requires the application of a fixed algorithm which can be learned. If you don't know the algorithm it's challenging, if you do it's not.

But that is not true of painting. Painting requires choosing a subject (for its subjective qualities) and then translating what you _want_ to capture about that subject and how you want to represent it in paint on some medium. You will also be applying a theory of mind and perception about the audience of the painting since you probably want it to appeal to them. All of these choices and the skill to combine them into a painting that achieves what you want is vastly more challenging than multiplication.

Multiplication is akin to paint by numbers.

EDIT: it actually strikes me that this conversation gets to the crux of why AI art is so polarizing. It depends whether you view art predominantly as being about the thing that is created or the process of creation.