He walked along with Jack, watching to see how steady he was on his feet. Just because he didn't want to replicate what made Jack the way he was didn't mean he wasn't curious about the effects.
He didn't know a Rose, but if he had to guess, he'd say she was the continuation of the long line of young woman that his Doctor used to always have traveling with him. So, really, it was almost like he'd met her already.
"She opened the heart of the TARDIS just to bring you back?" he said sceptically.