Good reminder on safety, IMHO.
FWIW, I also believe that "squib" loads can cause this same explosive effect in rifles and shotguns too....it is Blackpowder after all.
I've seen guys, "cutting corners" on powder, because, "back in the old days THEY didn't use a lot of powder, due to the lack of availability"....that's likely true.
I'm sure, or mostly sure, they didn't always fire the heaviest loads in their rifles on every shot.
But, I am pretty sure they would NOT drop their loads down to less than one-half, just to save on powder.....but, all this is just one person's opinion.
I can, however, tell you I didn't get this old just by shooting squib loads, and I've been shooting for better than six decades.
Squib loads are downright scary to me, no matter what they're fired in, especially with the newer patent breeches.