This is not an uncommon pose to a black bear or even for a grizzly bear. Bears are on the beach in the spring because plant food is relatively scarce during spring and bears will continue to loose weight until well into June. Plant foods make up the majority of a bear’s diet (sometimes, as much as 90%). The black bears are kept from the salmon rivers by the grizzly bears so the beaches remain one of their main sources of protein all year. I believe
this “back to us pose” is because the beach slopes down to the water line and it is easier to roll rocks downhill.