That would be an argument against PhD's; but physicians are, by and large, clinicians.
There is a good argument for adding a public health administrator or epidemiologist, but not a nurse.
There's no reason not to add a nurse to the team, but to replace a physician on the panel with a nurse - I just can't see how that would be a worthwhile exchange.
Maybe it's my lack of insight into nursing, but what would a mechanic know about cars that a car designer wouldn't? Especially that would apply at a national policy level?
I may be wrong here, I'm not an expert on nursing, but that's my thinking.