It you're asking seriously, no, a painting shouldn't ever be a called a deepfake. A photorealistic painting is called a photorealistic painting. The term deepfake refers to a type of thing, it's not a metric of some quality of an image, nor is it a reference point within such a metric.
A deepfake is a deepfake because it is a synthetic ("fake") image that depicts a real person/thing and is the output of a program that utilises deep learning.
A deepfake is a deepfake because it is a synthetic ("fake") image that depicts a real person/thing and is the output of a program that utilises deep learning.