That's sounds like the best theory I've heard so far but I'm still skeptical. I've only worked with simple embedded PCB components like resistors or an inductor

That's sounds like the best theory I've heard so far but I'm still skeptical. I've only worked with simple embedded PCB components like resistors or an inductor substrate, but in my experience if there are high speed signals anywhere near the passive, the design has to account for it from the beginning. There's a few clever ways to monkey patch unpackaged silicon into an existing board but AFAIK they all require access to some precise equipment to create a space for the wafer and wire bond it without causing some obvious physical modifications. Edit: Based on other posts in this topic, it appears that the chip wasn't embedded in the PCB - it was just placed on top of an empty footprint for recovery flash. If that's the case, then this hack is technologically uninteresting.