Xcel your response is exactly what I meant by the first statement in my post.
Just because your expectation is that a PPL shouldn't be able to fly a multi crew aircraft PIC (or co-pilot) doesn't mean the rules agree with you.
If you can come up with some actual legislation that prevents what has been stated I am happy to retract my statements, however you should avoid just stating what you think the law should be in the absence of any actual evidence.