Anthropologists moved away from Boasian decontextualized culture history, in fact, because it was inadequate to explain patterns of diffusion.

To explain, perhaps. To document, though… Without knowing that nearly all of the world’s words for tea (probably) ultimately derive from proto-Austroasiatic *la, we might never understand the early history of human use of the plant, and we’d lack key information regarding the nature of Sinitic-Austroasiatic interaction in prehistory (among other things). If you see Jurafsky’s book as an introduction to this kind of evidence and reasoning, instead of as a world changer (like 1493), then it probably works a bit better, and we can afford to be a bit more charitable to it.