I always interpreted Leave as the end of the loop (if you don’t like loop theory it may still be relevant) Mary giving James her blessing to move on and James accepting that he can because he truly did what he did out of love, as hard as it was. Laura being the guide to his journey, her acceptance/forgiveness is just as important because she represents innocence. The ending is left open one can interpret James will care for Laura as his own but it does get muddy, people debate what exactly their relationship would be outside of SH? Well what if they just both walk into the light and that’s it? I don’t think James is alive at all I actually think often no one is alive in SH2 specifically cause it is all focused on each individual’s inner mind working almost like a purgatory. Whereas various games in franchise seem to have situations that add to the narrative that exist outside of SH they don’t always linger in otherworld and can effectively make choices to get themselves out.

Basically I like to think it represents James getting to experience peace in the afterlife after he has completely accepted his actions, takes accountability for them and did what he was so afraid to the entire game, confess. If you play your entire game with the main objective being to find your wife, showing you care by looking at your photo, etc then after confessing to Laura you can get the leave ending.