The problem with that directive is that is still has a bloody large loophole in that a company can justify different terms and conditions between employees of the same position or grade. How they do this is not important because the simple fact is that they will justify it. Whether this is underhanded or not again doesn't matter. We all know it's possible to get around this.
The directive should have been geared to eradicate the possibility of different terms and conditions between employees with the same responsibilities. Good idea but tough to enforce.