It would need to be an historic backorder to make me switch from e.g. STM32 to like a C2000. Or honestly from an STM32F to STM32H.

For those how don't know, its very rare for a production device to use a socket for its MCU. Most MCUs don't even come in packages that support sockets. They're always soldered in. So unless you're switching to another MCU whose pinout, external clock, and power supply requirements are close enough that the hardware change is really just a BOM change, switching MCUs in case of a shortage is not a realistic option. Reportedly, some manufacturers were buying entire washing machines during the height of the chip shortage, just to de-solder the machines' MCUs and use them in their own products. That that is the better option should tell you how painful changing MCUs can be.

And that's to say nothing about porting the firmware, which may, or may not, be trivial.