STOVL carriers and F-35B changed to CATOBAR carriers and F-35C changed back to STOVL carriers and F-35B.
Eurofighter design requirement for a gun. No longer 'need' gun so decide to take gun out. Find the flight control computer needs the gun (or something of the same mass) so decide to replace with a block of concrete. Find it's easier just to leave the gun in place but not to use it so don't support with ammunition/training, etc. Find the gun has an operational value, so then support and use it.