I won't say anything about John Painter himself, his skill, authenticity, etc., because I have never met him, and it will be a useless guess with no actual proof.
The one thing I will say is that it is obvious to anyone who looks that the three pictures of his teacher posted by Shin have the same head, and expression, and that in the first picture, Painter has no shadow while his teacher and the chair does. Just an observation, and I am not saying anything about his authenticity or actual skill.
"Duifang jing zhi meng ji, wo fang tui zhi ce fang xi zhi."