Looks like there are docs that states RP2040's USB code is on an internal mask ROM, which can't be overwritten if true. The RP2040 don't have a user code storag

Looks like there are docs that states RP2040's USB code is on an internal mask ROM, which can't be overwritten if true. The RP2040 don't have a user code storage at all, and it resides in external SPI Flash, so those can be written over without having to have an all-Flash architecture. I've never seen other uC accidentally blowing out bootloaders, though. They have clever tricks that prevents write access on a firmware area while also allowing such firmware area updates. I suspect the author might have heard about some horror stories like AVR's intentional in-circuit programming disabling feature accidentally triggering due to configuration errors upstream to developers or sporadic errors in data transfer, which "just" needs requires +12V input to unlock. Presumably the 2040 won't have such gotchas that scares hobbyists.