They declare the skin dope myth of the Hindenburg fire "busted" because the skin alone did not burn but combined with the gas inside to cause the fire. However, this is incorrect since the skin dope theory never suggests that the gas played no role in the Hindenburg explosion. Instead it argues that the fire started with the dope and then moved to the gas. The Mythbuster's experiment confirms the skin dope theory since in their test of the combined skin and gas model the model burns in almost precisely the same way as the real airship did.
The Mythbusters are testing how the Hindenburg skin burns. In the comparison of the first two tests, Plain Cotton vs the Hindenburg bottom, the experiments framed are labeled backwards / incorrectly: Plain Cotton as the Hindenburg bottom and vice versa.