this page of the iNternet rabbit-hole, & note that all the Navy (& the one Coast Guard) admirals are officially photographed sitting, almost always w/ left hand over right hand, while all the Army, Marine & Air Force four-stars are standing, arms at their sides. No idea what if anything it all means, but there it is.
Something else we learned: The current Vice CNO is a woman-person of the African-American (& British-American) persuasion. We thought the Navy prided itself on being the most hidebound & traditional of the services.
Image at left from Life on the Home Front.