But isn't the video of them cutting it? Or is the uncuttable material underneath the bit that got cut by the angle grinder? I can't know if that's the material stopping at an arbitrary point, or something heavy underneath.
"An angle grinder or drill bit will cut through the outer layer of a Proteus plate, but once it reaches the embedded ceramic spheres, the fun begins with vibrations that blunt the tool's sharp edges, and then fine particles of ceramic dust begin filling up gaps in the matrix-like structure of the metal."
Because we can't directly see the miracle material, the video feels disingenuous.
Given that this stuff is half as dense as Aluminum, it's pretty impressive that the grinder behaves like it's cutting the most nasty steel (steel is ~3x the density of aluminum and much tougher).
If the plate had been aluminum, the grinder would have cut through like it was playdough.