You can really spot a fic's ambitions by which marriage bond trope it picks. The old-school 'Pureblood marriage contract discovered after the fact' twist is practically foundational, but it's grown into this whole ecosystem of variations. Some stories hinge on the revelation that the bond was willingly made during the war for, like, magical protection or political truce reasons, and now they're stuck dealing with the fallout years later. I've also seen a few where the twist is the marriage was actually public record in the wizarding world, but Hermione obliviated her own memory for safety, so the reveal is her digging through her own past. The suspense often isn't if it'll come out, but how—and who else knows. Lucius Malfoy secretly having the documents and using them as blackmail is practically its own sub-genre.
I'm more intrigued by the psychological consequences these twists set up. The magic forcing proximity or shared emotions can feel like a shortcut, but the better ones use it to strip away their pretenses. The twist becomes the starting pistol for the real story: two people who thought they knew their own history finding out they're anchored to their worst enemy, or maybe their only salvation. It's less about the wedding rings and more about the slow, agonizing, brilliant unpacking of what 'us' means when you didn't choose it, but maybe, eventually, you would.