The thing is, reflow is not why using left is slow. If the element is position: absolute, you don't reflow the whole page anyway. CSS transform is used because

The thing is, reflow is not why using left is slow. If the element is position: absolute, you don't reflow the whole page anyway. CSS transform is used because render is slow. With Servo-like GPU acceleration, render is not slow. Your suggestion would not be a good suggestion because using transform would be an unnecessary premature optimization then.