Here's my interpretation of Shots and Such route. This is still fresh in my mind, so feel free to reply if you think I'm missing or off base with anything.
The route diverges because Ashley is willing to shoot Andrew to save herself in the premonition. When Andrew finds out, he takes this to mean that he's not as irreplacable to Ashley as she is to him. He'd rather die than live without her, but to her, he's just a toy to be discarded.
This is, of course, completely off base, and the game goes out of its way to show how wrong Andrew's assumption is. Still, when Ashley again disobeys him and kills the campers, Andrew flies into a rage and tries to kill her. While resentment is at play, the operative motive here is actually possessiveness. He's given up everything for Ashley, and she can't even listen to a single thing he asks. Worse, he now knows she sees him as replacable. He's trying to assert that he won't let her get him killed and just move on. She's his, and if she won't be in life, she will be in death.
Still, Andrew does gradually come to his senses and realize he almost just killed the person he most cares about. So he tries to leave, hoping he can piece together what's left of his life, but also in the hope Ashley will be better off without him. How can he make her happy when he's failed over and over, and he even tried to kill her? Though again, possessiveness is at play here, since he thinks Ashley prefers the demon over him.
Andrew's escape fails, both because of Julia's growth (proud of you, Julia) and Andrew's own reluctance. He returns to Ashley, and the two have an intoxicated heart-to-heart where he both confesses his attraction and realizes that Ashley values him as irreplacably as he does her.
All might be well and good, but then Ashley finds out Andrew was in contact with Julia. Now it's Ashley who turns possessive, and while she's less open to reason than Andrew ultimately was, she also has more justification. Andrew did try to replace her with Julia, even if that proved entirely fruitless.
We've known since the voicemails in Ep 2 that Ashley feels insecure that her and Andrew have never consumated, and with Andrew's overt confession of attraction, Ashley's insecurity thus manifests in...dubious consent.
While Andrew wants to have sex with Ashley, he feels smothered by her, pressured into it, unable to say no. The resentment there can culminate in their double suicide, or Andrew can instead chose to marry Ashley. I don't doubt marrying Ashley is what Andrew wants to do, but Ashley's smothering insecurity prevent Andrew from making that choice freely.
Of course, we do see from Andrew's comments in the epilogue that, while drunk, he and Ashley did actually make love - only for Ashley to withdraw in the morning. It's not just Andrew who's having his desires smothered by his insecurities. I can only assume that Ashley becomes so entrenched in viewing sex as a means to an end to keep Andrew with her that the vulnerability and intimacy of love-making feels deeply uncomfortable to her.
This gives us a major clue as to what Nemlei is implying by her insistence that Burial -Questionable- isn't going the way people think. For Andrew and Ashley to have a healthy sex life, Ashley needs to understand it as an expression of love rather than a means of control.
Anyway, this route really upended the seeming trajectory of Andrew and Ashley's relationship. Burial -Questionable- seemed to suggest that Andrew and Ashley accepting their desires was the way for them to fix their relationship.
Shots and Such complicates the matter. By having Andrew and Ashley get together in a way that precludes addressing their greater insecurities, it becomes clear that while Andrew and Ashley connecting and working on their insecurities will naturally lead them to become a couple, becoming a couple in of itself isn't the end all, be all.
To some extent, it's not such a bad ending for a story as fucked up as this. They are together, their relationship is balanced enough, and they've accepted their feelings for each other rather than continuing to deny them.
Yet at the same time, the root problems are still unresolved. Ashley doesn't trust Andrew to stay with her, and Andrew is so deep in trying to please Ashley that he struggles to recognize his own desires.
If there is to be a better ending for these two, it would have to be one where both their insecurities are addressed and resolved. Having sex alone isn't going to do the trick.