Not surprising. The Party doesn't have control over AirDrop. In their opinion, AirDrop can be used to secretly disseminate information critical of The Party.
Remember, National Security in China doesn't mean the national security of China, it means the ability of The Party to remain in power. In The Party's mind, they are China (which obviously isn't true - China is bigger, and older than The Party and will outlast The Party), so any threats to their "stability" will be heavily scrutinized, especially if they are made by Western nations.
Remember, National Security in China doesn't mean the national security of China, it means the ability of The Party to remain in power. In The Party's mind, they are China (which obviously isn't true - China is bigger, and older than The Party and will outlast The Party), so any threats to their "stability" will be heavily scrutinized, especially if they are made by Western nations.