Good point. Might be nice to have some redundancy if a game controller is used for a mission critical component, but apparently, the US military approves.
The key here to me is they use it for periscopes. An important function, to be sure, but no one is dying if the periscope controller fails. That isn't the same for the controller on the submarine where it controls lateral movement, which is critically important when going near a shipwreck or other hazards.