A lot of your post is well-reasoned. The piece you're missing is that it would then be open season on every single borderline offside decision of the entire tournament. Busacca wouldn't taking questions from just the Nigeria press. He'd be taking questions from the press corps of a dozen other nations, asking why an offside decision in their game wasn't overruled. It would open up Pandora's box. So, no, I don't think Busacca and co. would be happy with O'Leary if he did this. The dumb luck (nevermind ignoring instructions and showing no confidence in your teammate) of getting one call right would not be worth the headaches of opening up about 50 other offside decisions to the question of "why didn't the CR overrule that one?"
He can't possibly see whether there he is offside since he is looking at the attacker with the ball. Also standing 10 yards upfield from the 2LD, it is almost impossible to judge if the attacker is offside or not. Even an AR who is 2-3 yards out of position may make the wrong call due to his bad angle. In most cases, including this one, the CR is not in a position to judge a close offside.