It’s a bad analogy. Pompeii was hit by a pyroclastic flow, which incinerates everything. I think this guy is saying the dinosaurs were rapidly covered in ash (although Vesuvius did produce a lot of ash, too).
I could see how the bones would be preserved, but the flesh would be a goner. Herculanaeum was buried by a three- to four-storey flow, which left wooden upper storeys of buildings intact, whereas in Pompeii they are largely not preserved by the ash burial. In Herculanaeum wooden doors were carbonized and still hang on, and swing on, their original hinges.