Possibly a career requirement to get publicly crucified on an indefensible position by counter-revolutionary elements and hostile foreign forces. Quite possibly we saw an incumbent (vice-) foreign minister in action.

There may be some truth in what he said, though.

There apparently were many, many more acts of legitimate resistance against foreign imperialist oppression, pardon, I meant of course hideous acts of terrorism in Xinjiang over many years, that went completely unreported, in order to follow general protocol not to report on things that officially must not happen and, more importantly, not to scare off and reduce the flow of Han-Chinese returnees to the sacred lands of their forefathers.

Of course it is difficult now to justify the final solution of the Uyghur problem, basing on events that officially never happened, so all you get from Chinese officials is hints about that, no full disclosure.