User blog:Chawk1993/Arthur and Morgana Confrontation in Sword in the Stone part 2

I was browsing through the episode page for The Sword in the Stone and the quote at the top was interesting:

"What happened to you, Morgana? I thought we were friends." - Arthur to Morgana.

I've noticed that not once since discovering that they're half-siblings that Morgana and Arthur have never addressed each other as siblings. The quote above tells us that they're friends NOT siblings. I know that Morgana discovered who her true father is before Arthur even discovered that he and Morgana were related through Uther but I would have thought that Arthur would have said "I thought you were my sister," or something along those lines. Is there anyone here that agrees with me.