If you don't want to wait for someone to answer, the short article has answers for all the questions you put forth so far.

I did read the article, but I don't see anywhere it states that there will clearly be one material on the outside and then a block of proteus underneath. What they are grinding is clearly two different materials, and it stops when it gets to the second one. The x-rays and the example don't seem to have a metal outside welded on, which is my confusion - it looks like someone welded a plate onto the miracle material, when in that little image in the corner of the x-ray it looks entirely homogeneous.

Because we can't directly see the miracle material, the video feels disingenuous.