The ultimate efficacy of these supercomputers depends heavily upon the programs they are made to run being able to split their tasks more or less equally across all the individual processors in the machine. A badly designed program or an ill-suited problem will leave almost all the processors idle.
And what makes you think they won’t have that? Recent events seem to suggest that the Chinese are becoming masters of cyberwarfare, or at least, better than everyone else considering all the practice they are getting...