When I saw this photo it told the story of the shape Arnold was in. This was the first call out for comparisons and Arnold wasn't in this group. There he is with his head down wondering why he entered the contest. Mike is smiling because he felt the call out meant those guys placed ahead of Arnold. That wasn't to be and when Arnold was called in later groups he rose to the occasion and stole the show.
How did Arnold manage to improve his middle delts, still sloped but very round and looks heavy, probably HGH helped him with his conditioning.
Even his forearms looks great, which was relatively mediocre compared to the rest of his arms (Mentzer is the king of forearms)
I find it stupid to call Arnold weak in 80' Olympia, he dwarves the rest of the lineup so badly, and he has fantastic conditioning, his legs are slimmer, but he is still ahead of the competition in general.