I had to think way too hard about what the author was trying to say. It smacks of an attempt at precise language, yet the subject matter is not precise at all. The author commits a Paul Grahamism, assuming their personal experience is generalizable and uniform.

Certainly, some artists work in the way they describe. Maybe even "most", who knows. But there are plenty of artists that do not. I've known plenty of artists to go straight to the detail in one corner of their piece and work linearly all the way across and down the canvas. I don't know how they do it, it certainly doesn't work for me, but obviously different people work in different ways.