By the way, how do you get into OS recovery (not 1TR)? `man bputil` does allude to a distinction between the two, as you mention:
> Boot environment requirements: software-launched macOS Recovery or 1TR.
The only way I know of to get to any recovery mode is by holding down the power button, which the man page says is 1TR (though I know you mention seeing that boot into regular recovery anyway).
Apple released a new platform security guide today. [1] According to that, there is a "fallback recovery OS" that can be accessed if you "[f]rom a shutdown state, double-press and hold the power button." I wonder if this one works if you zero the disk.
It also answers my question about the distinction between OS recovery and 1TR:
> Note: Apple uses the term One True recoveryOS (1TR) to indicate a boot into the primary recoveryOS which is achieved using a physical power button press. This is different from a normal recoveryOS boot, which can be achieved using NVRAM or which may happen when errors occur on startup. The physical button press increases trust that the boot environment isn’t reachable by a software-only attacker who has broken into macOS.
> Boot environment requirements: software-launched macOS Recovery or 1TR.
The only way I know of to get to any recovery mode is by holding down the power button, which the man page says is 1TR (though I know you mention seeing that boot into regular recovery anyway).