I tend to agree with you, Mike
I do not think that there are any bunkers in Scotland, for example, that I would class as "natural" today. Sure, some of them (but a pretty small percentage, IMO) were natural (i.e. created by wind and/or sheep and/or rabbits, etc.), but none of them that I know in any way resembles what a natural bunker is (if you want to see a few truly natural bunkers, look between the course and the sea at Brora, or in the wasteland central to the new holes on Dornoch Struie).
I haven't seen Sand Hills, but I would be surprised if the current bunkering scheme will survive intact after a few seasons of wind, rain and angry men with their niblicks. Not to say it will be worse, just that it will change, as all bunkers do over time. I know that Pacific Dunes is an amalgam of "natural" and created bunkers. Gene, do you really believe that all that you see at Sand Hills is as Bill and Ben saw it when they first visited the place? If so, that is really cool, and unique.....