These are percentages of enrolled students who majored in business compared to engineering. You have to look at how many of each major applied to conclude the major makes no difference. I bet there are many more business majors applying. While an MIT business major stands out, an MIT engineering major might stand out more if MBA admissions knows that engineering is much harder than business.
My points are made assuming your son doesn’t dislike engineering and can do well if he chooses it as a major. Whatever the decision, he’ll do well. That’s the beauty of having MIT on his resume.