OK, it is a big shock, BUT Xu is very young, ended last season in good form, is playing at home, and had a little time to concentrate on making gawd knows what other improvements. JUST don't trust young improving players.
Previous senior stats such as highest ranking wins are not hugely relevant with rapidly improving juniors.
My suspitions I'm afraid are that it's probably no more dramatic than that plus JoKo hasn't played well.
Of course, not that I wouldn't like to hear of some particular extenuating circumstance(s) re the match, barring serious injury / illness.