But maybe rapidly switching residential solar on and off in a coordinated way can also do funny things to grid equipment
The problem is that a few minutes is still too slow when a large power source suddenly drops out. The grid needs an immediate response, which can come from fast reserves such as batteries, hydro, pumped storage and other generators that can react automatically.
Pumped storage is basically gravitational energy storage: you pump water uphill when electricity is plentiful, then release it through turbines when power is needed.
I quite fancy electrical grid.
Hopefully mutually assured annoyance keeps everyone at bay.
same issue with large loads like boilers, this stuff should never be connected to the internet, but it is
if you can control enough load on the grid you can do real damage
In the end it's all about trust. Right now I don't see why China would like to burn down their market.
If that goal sounds stupid to you, that's because it is. I would expect some countries that are not China to act with such a capricious lack of foresight.