AFAIK one of the reasons phones typically leave logic like this in a binary blob on an IC is because the certification bodies stipulate that not only does a dev

AFAIK one of the reasons phones typically leave logic like this in a binary blob on an IC is because the certification bodies stipulate that not only does a device have to comply with safety standards, but it can't be trivially modifiable by an end-user to violate those standards. If you're marketing a phone where one of the advertised features is the ability to change the operating system, and the operating system is responsible for enforcing electrical safety, i don't really see how that's certifiable.