Balloons like the one shot down recently have a radar signal that shows like a search beacon.
They are easy to locate and track - stealth is not one of their features
And like most things that the CCP does, they saw an idea and are trying to see how it fits into an attack plan.
And speaking of Op Sec, the CCP is learning about our radars from building components for us, and developing or reverse engineering the radar software.
... more traditional radars that are oriented toward detecting fast-moving missiles and counterterrorism threats
WW II era radars did not use as much signal processing as we do today.
The software that controls modern military radars will throw out the slow movers as not important.
Since we are so tied to massive signal processing to find the blips among the background noise, a rewrite of the code is in order to find this new threat.