In my opinion, there is a difference to just sitting on the beach for the day or walking about or playing (longtime customary use) versus setting up an encampment for a week or more often on someone else's property (squatting) or on public property not designated for overnight or longterm camping. I'm not sure how the whole "what was once public land is public land in perpetuity" will play out in the courts. The problem with beach use became notable when the whole tent and excess junk became in vogue the last few years. The previous 50 years had people coming to the beach and having a great time. They did not set up tents and did not leave junk on the beach. Whether it was one person or 10,000. this wasn't the norm. Most people are really pretty cool about everyone enjoying the beach and just sitting on a towel or chair for the day. Even a small umbrella they can easily cart back and forth works. Once tents, sometimes quite large, and excess junk started cropping up and being set up for a week or more, and sometimes abandoned, the balance was upset.
I'm not sure if we are talking about the same "sand" provided by public dollars. I'm not a lawyer and don't have a bunch of lobbyists and lawyers at my beck and call to discuss the Supreme Court case. I thought that had more to do with some specific renourishment programs. I'm talking about county and other large machinery that plied the beaches after the 2004 and 2005 hurricane seasons, and later for other reasons, that pushed around tons of sand onto private property. That might be part of the ongoing Supreme Court case. I don't know.