This issue has come up a few times over the years and here's how I understand it. If a gun is C&R and it was dewat-ed (registered dewat), it is still C&R. If it was then rewat-ed, the C&R status doesn't change. This is different from manufacturing (pre-68) a gun from a pile of parts and a new or welded up receiver. These guns are not C&R.
Bob Naess at Black River Militaria is the guy that provided most of the insight on this issue. You may want to contact him.