Russia is much harder to penetrate for Chinese then US. Giving out secret like that is a death sentence, even if you manage to leave Russia there is a decent chance they will hunt you down and kill you in a very unpleasant manner.

US ability to recruit within Russia is also very limited. Something like that would not be picked up by sigint.

Russia did go all in on electronic warfare, I think US missed a golden opportunity to work with/through Ukraine to test their systems against Russian ones. If they could capture one it would be a gold mine of intel.