I was on the final mission of H3 and went to where the final grunt (the cool story bro achievement) was but when I got there one of the sentinels killed the grunt. And I’m like great now I’ll either kill myself or restart the last checkpoint, so I walked off to kill myself and then the achievement went ding. I’m like WTF!? How was that even possible to get the achievement without completing the achievement? I got robbed from a freaking sentinel for killing the grunt and I still get awarded. Has this weird thing happen to anyone else?
Maybe the unlocking was triggered as soon as you got to the Grunt, and showed up when you walked off.