I’m just going to imagine there was a scene when the family was gently taking Stan through his memories and helping him remember, and they get to the part where he stopped Bill.
And they explain how brave and daring he was, but none of them know exactly what happened in Stan’s mind, so they don’t know the conversation he had with Bill.
But Stan does, and he smiles when he starts to remember, that same resigned but happy smile right before the flames consumed him, and he repeats, without really considering it all,
“Heh. Guess I was good for something after all.”
Everyone pauses and looks at him, so very concerned, and Stan blinks, confused because he know that’s how it happened - at least, he thinks he knows.
He feels a hand on his shoulder, a six-fingered grip that’s slowly starting to become familiar once more, and it turns him towards a face that he recognizes as his own but the only name he can put to it is Ford.
Ford says, very carefully, like he’s holding something back a whole whirlwind of emotion, “Don’t. Say that, Stanley. Don’t ever THINK that. You didn’t need to sacrifice yourself to become good. You were already good, just the way you are.”
Mabel and Dipper nod emphatically, curling closer to him. Soos lays his head on Stan’s.
Stan frowns, puzzled. “But that’s how I remember it,” he insists, quietly.
Ford smiles at him, and it’s a sad smile, but with an edge of hope.
“Well, your memory’s a little wrong in some ways,” he tells Stan firmly, winding an arm around his shoulders, tugging him near because he’s not ready to relinquish what he so nearly lost, not even to his brother’s own inner demons. “But don’t worry. We’ll help you fix that. We are your family, after all.”
And Stan, while he’s not quite sure of anything at the moment, feels positive that that’s true.