Yes, I knew Bill Moran well, and the man who wrote the book, Wayne Holter, was an old and very good friend.
One of the points about Damascus was that it was not one material. They started out as rods of iron and steel, which were heated white hot and twisted together. Then they were hammered into rods of a square or rectangular section before being heated again and wrapped around the mandrel. Upsetting, as is shown in the video, was done to the breech part, but the forward part was usually just welded together by pounding the white hot strips.
One of the problems is that even the best welding left tiny gaps between the strips, and over the years, corrosion from primers and black powder was forced into those gaps, corroding the barrels from inside. I have sectioned some old Damascus barrels (admittedly not of high quality) and found the inside a mass of black and orange rust, sort of like orange lace. One of those barrels let go and took parts of three of the owner's fingers along for the ride.
Rifle barrels are generally thicker so the main danger comes from shotgun barrels. And part of the reason for that is the different pressure curves between black powder and smokeless. Black powder has a quick ignition and a rapid drop-off of pressure, which means the pressure is mainly contained in the thicker part of the barrel. Smokeless powder, even if the maximum pressure is no higher, is progressive burning, meaning that pressure remains high out to the point where the barrel thins down, which is right where the shooter's off hand is positioned.
Some people will insist that Damascus (twist) barrels are OK, even that they are stronger than solid steel barrels, and often will point out that they passed proof tests, even though that was when the gun was new over a century ago. One man claims he has fired thousands of Magnum shells from his English double gun, with no problem. All I can say is that I do not recommend it.
I trust the above might show that even though some of those guns were strong when new, they might not stand up to firing today, even with black powder loads.
Jim