Mahalo for your questions and I believe this is a topic that needs to be explored.  

In my opinion, a Hawaiian should not get a pass simply for being Hawaiian.  If I may elaborate upon that.  I am Native Hawaiian, but I am not a hula practitioner.  I practice quite a number of traditional customary practices, but hula is not one of them.  

I would never use any of the art forms - that I dabble in - to express my own perspective of hula and to declare that perspective as being "distinctly Hawaiian" or "authentic."  There is absolutely nothing "authentic" about a non-practitioner's depiction of that practice.  

I cannot say that a non-Native could fluidly adopt every Hawaiian cultural practice, but I know for a fact that non-Hawaiian hānai children have, in the past, adopted the culture of their adopted parents and successfully perpetuated those practices.  It is possible.  

In the case of the architect that profited from this "art," it's probably not likely that he's a practitioner.