Seems like the authors are finding loopholes to write incest

Always have been. Honestly they should man up and write proper incest and make it psychological/ SA abuse and it's after effects of they want to write incest so bad. Maybe then the story would have some depth to it. Not promoting incest, just saying that a story would be interesting (not nice, interesting) ofc it's a heavy topic, but the aftereffects and symptoms of getting SA'd or being in an insestuous dynamic in early age and it's harm on brain, that can be dissected through it.