> So in theory, he could make another access road further down and leave that one open?
I'm not sure about the law in the US and California, but in some jurisdictions you can't just move an easement. There was an easement running through his property from the road to a specific point on the beach. He can't just move the ending point of the easement to a different spot on the beach.
Still doesn't explain all the houses and cars directly on the beach. Does he own all those houses too?