If you anchor in a designated anchorage, then the ball isn't required. Most of the sailboats I've seen anchored didn't wear the anchor ball. The big yachts (mine was 45m/145') always displayed the ball.
I've seen very few inverted cone "motorsailing" day shapes. The joke in the schools is that this particular shape is on the books
but never seen. While 0.6m seems very large for a 13m vessel, it's a good idea as many motorsailors will have sails
up. The day shape gives approaching vessels an earlier indication as to the mode of power.