Wait, I'm confused; is Sterling like a Trinity or something??? Because the publisher writes that the Trinity IS arrested, but then says THEIR best friends - what is going on here?

Oh ok, I kept on reading, it has to do with gender wars... but that still doesn't clear it up. If Stirling's pronouns are they/them, wouldn't ARE be the correct way to address them at the start of the sentence? As in "Stirling are arrested..." As in "They are" not "They is"???