As the video shows, when you kill an enemy with Golden Gun while wearing Celestial Nighthawk it doesn't always 33% of your super bar. I've done a few tests and can confirm that it is not a bug with shielded enemies and it is not a case of killing an enemy at the same time as another player. I'm not sure what causes but letting the dev team know. Edit: After further testing, it seems to happen more often if you fire immediately after activating GG. It's not 100% of the time but it's fairly frequent.