Think about it: MBAs learn non-engineering skills, so how could it possibly be otherwise. If you get an MBA and continue engineering work, then by definition you're not leveraging your MBA, and vice-versa. That's a huge simplification, of course and I don't completely agree with the OP, but that's the gist of her point.

There are exceptions to every rule, but I'd say within the context of "jobs at existing large employers of MBAs and/or Engineers" the true intersection of engineer & business is nonexistent.

(There are lots of places where it'd be advantageous to have both skills, but never necessary, which is my underlying thesis.)