Personally, I think this was one of the most defining moments of this episode. Yes, Gallifrey might still be out there and John Hurt’s War Doctor gets redeemed even though it’s self realized a few regenerations later. But this is one of the most important moments.
The Doctor has a reputation for always having a companion. Yet, the Eighth Doctor died and regenerated after being rejected and to our knowledge, the War Doctor had no companions. It’s not like it was for a short time either. It was a much younger version of John Hurt that started off and since the Doctor’s aging isn’t always consistent, we don’t know how long he was alone.
So here is the War Doctor, fighting in the Time War for who knows how long and he’s alone. He’s not only not the Doctor because he made the choice to be a warrior instead, he’s not the Doctor because he’s alone. What did Donna, Amy, River and others say? That he shouldn’t travel alone.
While this episode started with Eleven and brought in Ten, it was really about a journey for the War Doctor and in his final day, his final trip, when he was finally not alone. He had the Moment/Bad Wolf and Clara but most importantly, he had himself. In his loneliest hour, the Doctor was able to be there for himself, be the companion when no other could be found.
They scoff but really, that was truest definition of Ten and Eleven in this episode.