I'm surprised by the writer completely ignoring the possibility of blast injury to the lungs...? Blowing into a hose connected to a space in which an explosion takes place would worry me much more than what the lid might do.
My naive assumption is that there’s a combination of two factors going on: 1) the blast force will be proportional to the area through which it’s transmitted, and a narrow hose will have a lot less area than the lid of a can, and 2) if the hose is fairly flexible rubber, there will be significant reduction of the force over the length of the tube.
All of these things are possible, but personally I'd just never risk it by assuming that the pressure wave will escape "somewhere". Call me a coward, but still...