Earlier quoted context omitted.
You're looking at it the wrong way. The point of the regulation would be to force manufacturers to officially give users the same level of code execution that they have over the sold devices as themselves. If Apple, via software updates, can control what software runs on the iPhone of the user, then the user should also have that control, to install whatever OS/bootloader they desire, the same way as Apple can.
You're shifting goalposts. You were arguing for the same level of code execution after sale of the device , not at point of compilation. By the time every iPhone leaves the factories in China and India, they're already locked down. The consumer only has as much ability to execute code as any bugs allow in the initial OS release. Also, Apple doesn't have the ability to install any OS/bootloader as the hardware is spec…
The code execution is locked down with a private key that only Apple has.
Apple can therefore sign any executable for any iDevice that exists, and it will run without issues. They could make a completely new bootloader/OS combo from scratch while mantaining compatibility with the hardware.
The bar is then: "Is it technically and officially possible for Apple to install any OS/bootloader that's compatible with the iPhone hardware?" The answer to that is yes, it is.
So, if it is possible for Apple to do so (by them having the private key used to sign the OS images) even after they sell it to me, then it should be legally mandated for me to have the same level of official posibility to do the same via the same means.