They chose to come down over the ocean for safety reasons, and I doubt Starship was designed to float.
This wasn't a Mars landing analogue mission. It was an orbital reentry analogue mission, so it was a success. Also, the Titanic was a fully operational watercraft, not a developing Spacecraft.
SpaceX claims this based on goals they set out beforehand, unlike how you decide the purpose of their test afterward. Also, they landed SN15.
I don't think the FAA has even disapproved the vehicle for human flight.