US warplanners considers sending 100,000s of bombs on PRC mainland targets in case of TW scenario all the time. Is that 10D thinking? It's basic escalation dynamics of recipricating homeland attacks with home land attacks, the difference is up until recently CONUS has been shielded from both precise and volume of long range strikes from her adversaries, largely due to technologic limitations, enabling US to project power with impunity. This is PRC incrementally establishing mutual homeland vunerability to deter US from messing in her back yard. It's trying to deter US from intervening in TW by raising costs to CONUS, just like US is trying to deter PRC from moving on TW by raising cost to PRC mainland. Except until recently, only PRC had to factor in homeland attacks due to asymmetric US power projection capabilities. More and more, and for the first time since revolutionary war, US now has to factor in serious homeland attacks with respect to PRC. Demonstrating CONUS is vunerable, especially if it influences public thinking, is as strategic as it gets. Lots of Americans are still operating off the notion that Fortress America is impervious and US mil actions abroad stays abroad, and generally that's true, until it's not.

Ability to generate simultaneous bandwith of 100,000s of fires is also significant, most conventional long range strike / projection platforms are severely limited in how much fire they can deliver / unit of time. It's not feasible to sortie past limit of carriers or air bases, but the amount of balloons (or land based missiles) that can be delivered is much easier to scale, which means it's easier to satuate defenses. At the end of the day PLA is going to have very limited traditional methods of projecting power to CONUS (lack of carriers, or local basing), so they're going to latch onto any asymmetric platforms that can reliably bring war to CONUS. TBH I was not really anticipating mass balloons, and PLA planners probably weren't either. But the idea of hitting strategic targets with expensive long range missiles (i.e. prompt global strike) is something PLA is pursuing, now I imagine PLA planners are likely going to explore the virtues of cheap balloons that can scale more economically than missiles.