Other than FC playing with the Shojo aspect of Estelle's hot 'n botheredness flustering her partially for laughs, the theming of Estelle learning to think first, conciously be the shoulder to lean on, for Joshua to trust, to quite honestly believe himself WORTHY of love and that he's not this spike of darkness that can only eventually bring harm to his Estelle (who shines like the sun) the longer he's with her when more than the most mundane of danger appears.
Remember their character trajectories over the last two games: it's why Estelle is stronk in the face of bewitching dreams and bad mans out-of-left-field recruitment pitches. It's why Joshua's "broken doll" act he put on in early SC was both where he retreated to and why it was so painfully obvious to even those Capua doofuses. Even his really nasty backstory deep dive on the escape ship does nothing but encourage the best words out of Estelle this time.
Even at the time this happened, showing off how his thoughtfullness and silver tongue made him out to be the diplomatic of the pairing...
you had the farm scene where she talked him down from his darkness. That was the culmination of that, bringing this fact out into the obvious open, for the player, for Joshua, and well, even Estelle. They earned that happy ending, they were each others pillars, and love conqured all the RIGHT way.
They finish each other sentences, they finish each other's lunches, they're far FAR more chatty and "complete" around each other. It would be far wierder for them to do any of these lengths and tactics as siblings (and we really TRULY don't need any more of that in anime).
