So the problem with the kill switch is an age old one: the weak point is the people, and it's gonna be reaaaaaaly easy to bribe the folks to simply not pull the switches, or disconnect them in advance.
I've worked with TSMC in the past. I've been to Taiwan, I've had a week's worth of starbucks coffees from one of the Fab 12 building's 7'th floor kiosk in Hsinchu city. Let me tell you about the culture there.
More than 2 decades ago, we came in with what at the time was cutting edge Big Data analysis software we'd created. Now a days it'd be called machine learning or AI, but back then, it was Big Data. It could track down issues and correlate cause and effects with semiconductor data. Hey, you've got a common short on layer 12 because of copper growth issues with your scrubber pass on layer 6. Or in one case, when operator #3401 is logged into the transport machine, yield goes down by 12% and the number of scratches, closed vias, and particulate defects increases by 6%. Good stuff.
Anyway, we bring our software in, do a demo - which takes about a week - and our point of contact could not care less. He tells everyone that we're unnecessary, not needed, he can do what our expensive SaaS does, himself. So we have a little challenge, blow him out of the water, and that's after he stripped OUR data of identifiers, so we can't tell if the data is a voltage test or resistance or defect identifier or whatever. Anyway, he stays in the meeting to discuss things after the presentation of results, and comes out later grinning.
We go to pack up and he's got 4 guys with him - "You can't take your laptop out of the building," he says. It's had their data on it, even anonymized, and they believe it's a security risk. We might be spies. They caught some last week.
Now while we were there, we had to run all the analysis from the laptop, which remained on site, locked to a table. One night, we found our analysis was interrupted and the hard drive had been removed while the system was still running. They had made a copy. Tried to steal our software.
But we knew this was going to happen. This is how things work in Asia, and our code was CPU locked, so it wouldn't work without a lot of extra work. So by the time we were ready to leave, they realized they needed the laptop itself to run it. Or maybe it was just easier in any case. So we said we had to wipe it to protect our IP, which they had no problems with. So we got out our tools, and took the motherboard and hard drive out and ...
"What are you doing?!?!" - one of the folks left to watch us cried. "Oh, we're destroying it so it can't be used." "YOU DON'T NEED TO DO THAT!" he shouted, as another one sprinted out of the room to get the manager. I'm drilling through the cpu when he gets there, his face bright red, "This isn't necessary" he says. "It's okay, we don't mind," we respond. "We want to make sure no one can use our software."
He kept trying to get us to stop, saying how unnecessary it was, and I'm pretty sure as I was snapping the hard drive disks with pliers that he was crying - either from fear or rage, I don't know - but that was that. We declined their literal spyware-laden "replacement laptops," and noted how the two non-special-software laptops which had been used to create the presentation and had also had data on them - were not included in the 'keep' order. ...
The purpose behind this story is to note that the overwhelming mindset in that area of the world is deep, fundamental and systemic lack of morals. If you can steal or cheat, you do it because it's a moral imperative to take what you can. It's at every level, in every aspect, from business to business like this, or business to personal; corruption, embezzlement, graft & kickbacks (I've got a whole story about "red envelopes"), and in this case, outright blatant theft.
It's basically a hustle culture turned up to 11.
So I have no doubt that if China were to invade, you'd find these kill switches surprisingly non-functional or simply never used, because the folks who would use them were already well paid not to.