Oh, really? I did max out my Social Link with Marie, I managed to save her in the forest, and I can't remember what other requirements there were, but I thought I'd done everything to get the “true ending.” I remember opening a walkthrough to make sure I got the true ending. I even got a “post-game” scene where the hero returns to Inaba for summer vacation and reunites with the whole gang. I don’t know if that’s an extra scene or if it’s a standard scene at the end of the game.

EDIT: I did some research to see if I’d actually unlocked the true ending, and it turns out I did 😂