Nothing to do with increased security for the 19th Congress.

Nothing to do with being a journalist.

Everything to do with not presenting yourself at the Chinese police station.

Source: Lived in China for years, was forced to write an apology to China for not presenting myself after moving to a new city 2 months later (had a work visa); my communist party member landlord smoothed things over with local police. Obviously Jon didn't have enough guanxi.