I'm just surprised they didn't try to make them double agents or at least feed them false information. It seems like a rash judgement to suddenly eliminate 30+ people who you know are spies.
It isn't a rash judgement if the CCP is so confident of their counter-intelligence program, that they evaluate the effort of neutralizing with disinfo or turning those 30+ is not worth their trouble and informational value. Considering the scale and depth of surveillance they employ within China, and continued heavy investment into more, I wouldn't want to off-hand rule out that possibility.