It's still a weapon, and generally you don't want to distribute information about manufacturing weapons. It also highlighted the relevant keyword to convey the mechanism.
A knife is a weapon, and the way to manufacture a knife is to sharpen the edge of some metal.
A Molotov cocktail is maybe ever so slightly more complex to describe/understand/imagine? I think if you've ever seen a photo or description of one, or thrown one in GTA as a child, you know how they are made. The overlap of people interested in making one and people not already knowing how to make one is surely approximately nil.
