Source: over one year working on reverse engineering this precise platform almost full time.

Also, if you've spent 23 years in the semiconductor industry, I have no idea where you're getting the "not connecting metal" story. Nobody does that. How would you even do that for a yield issue? That doesn't make any sense. Chips that have failed bits get the broken parts marked bad via eFuses after production and the initialization logic or bootloader will then read the fuses and power/clock gate those bits and lock them in that state, via existing isolation/gate logic. That's how the entire industry does it. Metal patches are for fixing design bugs in a respin and stuff like that, not for turning things off in a finished chip. And you certainly wouldn't make a change in the line to the metal to disable half a chip from the get go. That's just throwing silicon away for no reason, why wouldn't you try building the full thing first and seeing what works? The entire concept makes no sense.