Idk if this person used textured brush for the hair, it looks like a bad photoshoped picture of hair just pasted in the area, next time try to use a single regular brush, it may take longer, but will look better, And the way the head was shaded it seems like one picture that had lines before but at the end they didn’t made it to the final piece, perhaps try to work more with the shading using darker tones to define edges better