I think he must have left a bit out. To make it explosive, typically it needs to be in a space that will allow it to compress when ignited. That can be a hole in the ground or a large quantity in that it will create its own compressive reaction. Also generally to set it off, you generally need a shock wave type of igniter. A small amount will simply burn.

Dynamite is same way. I worked with it quite often when younger. Old dynamite can begin to sweat and when like that, it is a bit unstable. Few times just burnt it to destroy it. Otherwise you would need to use a blasting cap to set it off. That was now expensive and might annoy neighbours if you do it above ground.