My take on the 333 is it's an exemption from rules that are not formal. By getting a 333 the receiver of such is admitting the proposed FAA rules are in acceptance. Regardless, if that is so or not, my take is that the 333 does not give a sUAV an air worthiness certificate. Having a pilots license (certificate) of whatever rating does not automatically provide an air worthiness certificate for an aircraft, in this case, an sUAV (is it really legally an aircraft?). A pilots license and an air worthiness certificate are two separate pieces of paper and are not related. An individual can have both or either one without the other.
My input on this is as a result of my knowledge of it, having built a high performance experimental aircraft (Lancair), getting it FAA inspected, and receiving an airworthiness certificate, which by the way, requires a certain number of flying hours (25 or 40 hours depending on engine/prop used) in a specified flight test area, by the inspector, for its phase I testing.
I may totally wrong in my interpretation, but until I read official government documents otherwise, I believe this to be so.