The dolphin ring link is particularly striking to me because I've always seen Turner as somewhat unique among modern writers - I don't think anyone else right now is writing stories quite like what she's writing. But the ring ties her specifically to Rosemary Sutcliff and more generally to an older tradition of historical fiction with these heavily fealty-based relationships - I'd say D. K. Broster writes in the same mold, and some of Mary Renault's ancient Greek novels are similar.

(Turner's innovation is the make two of the main fealty-inspiring figures into queens. In fact, the first king on the scene, Sounis, seems notably unable to inspire this kind of allegiance.)

IIRC The Thief was Turner's first novel (she did publish a book of short stories earlier) so there couldn't have been any guarantee she'd get to write any sequels. There is a whole scene in The Thief where Gen meets Attolia, so there's an opportunity for some pining right there, but if it had ended up just being a standalone a Random Pining Scene would have felt really weird.