Okay, let me reformulate my question, why is this even a thing people are complaining about???
Twins =/= Siblings. Trolls don’t have familiar structures because, specially after the Rebellion with Adults being off the planet, they don’t tend to group together in the same way Humans do. Trolls CAN feel familiar bonds as seen with the Dolorosa and the Sufferer, but they’re extremely rare because it’s just not something that happens with Trolls between Caste Differences and the World they live in. But that doesn’t mean there can’t be Twins. The Troll Genome seems volatile and mutable enough as is after all I would’ve been more surprised there weren’t Twin Trolls at some point.
And of course they share a Lusus, they’re Twins, arguably genetically identical and hatched from the same egg, they would be chosen just the same by the Lusus. And if they do share a sibling-like relationship? Their unique case, much like the Dolorosa with the Sufferer, would easily explain why.
Fandoms have been extremely quick on criticising authors for ‘bad canon’, ‘forgetting stuff’ and the like lately, as if they were the expert eminence on everything that’s ever happened in Canon. Look, mixing Fanon and Canon is fine, but don’t go around feeling superior because you prefer your Headcanons over Canon or misjudged something as Canon when it was never truly stated. The Overwatch Fandom is a huge offender when it comes to this stuff, and I’d hate seeing it bleed into Hiveswap and Homestuck more than it already has.