It makes sense. Updating the hardware is logical due to magnetic medium degradation. There’s no reason to run a current OS on a closed system. Features are irrelevant. It’s all about stability and security.
I’m very happy to see the Navy running on old hardware. Do you really want the “move fast and break stuff” tech bros designing weapons!? Plus, this is the same week where businesses running Win3.1 dodged the biggest computer outage in history.