"Apparently, the liquid metal had corroded the processor's integrated heat spreader (IHS), removing the chip's markings, including the processor model, batch number (FPO), and 2D Matrix (ATPO)."
Not fully true. The directions to use liquid metal means you have to 'scratch' the surface of the IHS. They usually come with a little scrubbing pad to use. That in itself is considered "physical damage". And scratching off the Intel markings that help them identify what the CPU is, batch #, etc, yea, I can easily see Intel saying no for an RMA.
Now, I'm not a scientist, so I may be corrected on this, but liquid metal itself does not cause corrosion. However, it can definitely cause corrosion if you use it in a custom water cooling setup with a copper heatsink and aluminum somewhere in the loop. (I'm not sure if that's just with liquid metal, or for everything. I think it's just for liquid metal though).