nothing much wrong with his back ...... he just couldnt fully spread and contract his lats...same as his lack of control over every other muscle group.....
if you look at his front double biceps pose u can see the thickness in his lats from the front and his taper...
also standing relaxed from the back u can see his lat development
and his inner back thickness is great too....seperation between his lower traps and rhomboids and lats is very good too....