As to the Tower of Joy being in Dorne, I’m not sure that your external/real world explanation works, either. I’ve not yet seen any particularly essential story reason that the Daynes have to be Dornish. Maybe the Darkstar is going to have some indelible impact on the story, but Arthur, Ashara, and Edric would work just as well being Marcher Lords in the Stormlands, wouldn’t they?