Do they give the reason for why that might be case of such use of perfective here ? Just curious.
If I’m remember it correctly, the above ‘aspect’ can ( also ) be interpreted something like performance error, where one speaker just copies the form of another one’s question.
If we paraphrase the first one like “ I’ve lived in China for six years but came back in 1999” that would clearly be the case of adverbial incompatibility as for ‘in 1999’.
In the second question, the second speaker seems to ‘pose’ the perfective question all “by the book.”
( both recency and resultative aspects might be implied , he’s not sure whether that someone still works there or not ) The same analogy goes for the first example as well, in my opinion.
Maybe there’re other explanations but I can’t think of any readily available as for these examples.