I agreed with your Man of Steel explanation. But in the sequel Man of Steel 2, Batman Vs Superman, the intelligent level of Superman is seriously derailed, when Bruce Wayne used Krypton Gas Grenade on Superman the first time, we can interpret it as Ka El's arrogance at work thinking it's just an ordinary grenade and arrogantly goes headlong into it, anyone who survived the first grenade attacked would have grown wiser, Superman as a perfect Kryptonian due to the codex surely learnt his lessons. But he suffered a second grenade attack again, disabling him again. That fight scene is just plained stupid. With his superspeed, he can definitely catch the grenade in mid air without impacting it. And with Superman dying at the hands of Doomsday, a mindless zombified Zod just goes to show Superman isn't stronger than Doomsday by too much. And Superman had Wonder Woman on his side in the fight too. All this story was concocted by Snyder himself, so as a whole, the two movies are seriously contradictory by the same producer. That's why, Man of Steel story and wonders were ruined by events in Man of Steel 2.