The sea wall that blocks the view of the ocean (just like the one at Royal Cinque Ports) is there for the same reason - strong winter storms that virtually destroyed each course.
As far as I know, the holes across the road are not Mackenzie's. Good thing because they are rather poor.
The original Sharp Park course had several holes right along the oceanfront. They didn't last long; a big storm a couple of years after the course opened flooded it with seawater, and necessitated the changes.
It's not possible to lower the sea wall; the last time I was there, last winter, the waves were breaking pretty close to the top [and right onto the street along the beach to the north, where the sea wall ends]. Three of the original holes were actually UNDER the present sea wall, so it's not possible to restore those, either. And one of the present holes has had to be abandoned due in the settlement with the environmental lobby protecting an endangered snake ... the environmental group wanted to shut down the whole course over that, and it took a decade of court battles to stop that.
The group that wants to restore the course knows it cannot be fully restored, but would like to restore as much of MacKenzie's original plan as possible, with the holes across the road replacing those lost to the sea wall. I've been advising them for a few years, as has Jay Blasi who lives out there. There is some light at the end of the tunnel to restore the golf course, but it's far from a done deal yet: it remains to be seen if there are so many restrictions placed on the work that we have to decide it's not worth doing. The combination of bureaucracy and litigation involved in working on the California coast is just mind-boggling. Dr. MacKenzie would have a conniption fit if we had to explain it all to him.