He also beat Jackson twice who hit harder than GGG. GGG has nothing on his resume that suggests he beats G-Man imo.
He was green for the early losses. GGG hasn't fought anyone remotely as good as Jackson, Mugabi or Benn. I'm not sure Golovkin beats those three either, he could chin Jackson but may get ko'd himself.
G Man had incredible power but was also easy enough to hit. This would have been an interesting match up. Could have gone either way.