I don't understand the point of this scene. 
I've been going through it all in my head and it didn't reveal anything new or... anything. 

Can someone explain to me the meaning/relevance of the after credits scene?

It keeps people from making threads with theories of Phelps surviving? 
  
But seriously, there's probably some meaning behind the funeral and all the dirty cops pretending that they were Phelps' friends.

It was just showing what happened when the 6th came home, and Courtney decided to steal the morphine.

I don't think it is meant to explain anything about the odd ending before the credits, just a bonus.

It reinforces Kelso's good nature.

I also don't understand why some have called it a critical/essential scene for the overall story. I assume people say that because it reinforces Kelso's good nature, but I never doubted him. He never once showed anything that would have me question his good nature and I felt like I wasted my time sitting through the credits for that. I am glad they didn't pull a "I won't say the game for potential spoilers" and have Kelso in on it the whole time because that would have been ridiculous. In all honesty, what they ended up showing was pointless.

It reinforces Kelso as a genuine guy, who wanted no part in the drug affairs that, in the end, became a major contributor to the corruption and Phelps' downfall.

It pretty much reinforces Kelso's comment in the end, that he was never Phelps' enemy. He never had any part of it, even if he had a lot of reasons to stab a knife in the man.

It still strikes me as though the entire story was a setup for a sequel featuring Kelso. That final scene, in particular, along with Kelso getting picked up by the assistant DA ...
 
Very odd. It's like they didn't really know where they wanted to go with things, and so tied up with Kelso rather than Phelps. Lots of very strange decisions were made in how the writers approached the story in this game.

I hope they set up LA Noire 2 with Kelso becoming a private detective.

If I'm remembering it correctly, wasn't the idea to steal the morphine part of the reaction the men had when they heard about Phelps being honored and all that? The point of the scene was to show that the events that led to Phelps' fall were all unknowingly set in motion by himself.

If I'm remembering it correctly, wasn't the idea to steal the morphine part of the reaction the men had when they heard about Phelps being honored and all that? The point of the scene was to show that the events that led to Phelps' fall were all unknowingly set in motion by himself.

It reinforces Kelso's good nature.

The big thing I took away from that last scene was the fact that a conversation about Phelps is what led to them stealing the heroin. Sure, knowing Kelso isn't dirty is nice. But the fact that Phelps is a victim of his own success is a far more interesting thought.

It was a nicely written and shot scene, to reinforce the characters of Kelso and Sheldon, and probably as a little closure, getting to actually see the origin of the heist. Nice little touch - if it was a movie it would still be a post-credits scene.

Also, the writer's didn't know where to go with the franchise? Please, this script was so deliberately written and they made so little compromise to gaming conventions that I don't really see the lead writer and director starting Team Bondi and Image Metrics, investing millions, specifically for this game and then rush the script at the end for an easy second protagonist. Especially when Cole and Kelso where set up for this story arc from the start. On a side-note though, I'd love a sequel with Kelso. And I know it's not going to happen, but I'd love it more if they moved on to a different setting and a new game or franchise. Treat it like art and not just a business asset.

The point was to demonstrate how Phelps caused all the problems. Was because the Phelps promotion that the marines  decided to steal the morphine. Phelps fucked in the war, fucked with the marines mindes, cheat your wife. It´s fantastic how we play a hero and in the end we see how he is a fucked man in every way.