"He didn't want to." John looked down at their joined hands and gave hers a squeeze. He quirked a wry smile. "She didn't want to at first, it took a while. In fact, I think this relationship, between you and me, is more stable then theirs - at least at the point I left."
There was no hesitation in using 'theirs' or 'she', both John and the Doctor found it far easier to differentiate between their lives on the island and the versions of them back where they had been taken from. It was just in their nature to adapt to, accept and understand such situations.