I would add, that there are just weird occurances where the metal is fatigued or flawed.
What sets this door apart is that it has composite armor plating, reinforced with a laminate honeycomb in the middle, followed by a second layer of composite armor plating. 10cm or 3.9 inches of reinforced concrete is not thin by any stretch of the imagination, when I think of concrete bunkers though we are talking feet thick (reinforced). The difference between structural materials is pretty vast. At one end of the spectrum you have cinder block, makes for a good structurally sound building, but I have seen video of an Uzi on full auto (standard ball ammo) just devastate it. Standard residential construction, 2x6 wood frame, vinyl siding, vapor wrap, 3/4" sheating, insulation, and drywall, excellent structurally for its purpose but I wouldn't consider it cover...good concealment though.
Current material engineering leads me to believe that there are some very promising lightweight materials out there that have excellent potential as armor. So I am extrapolating, but I don't think that I am out of the realm of possibility in thinking that two sheets of 15mm thick composite armor using carbon nanotubes and other materials would be pretty darn tough. There again though, I would like to think that I am open minded.

Sound off people, 24 AR or lower?
Edit: I would certainly be willing to concede that a cutting charge (think RO Blade) would probably have little problem with this door though.