I think that's a fair statement in isolation, and I do find Blow's grandiose and loose use of language to get in the way of his message, but I believe the point stands. The knowledge was lost and that is the part that is most relevant here. The factors that caused it, be it the the 'collapse of an empire' or just one illiterate glassblower's creation not being documented before his death (or any other of the tremendous number of reasons) are less material than the fact that we have a chaotic system where we're trying to stop entropy.

To that end, I don't think he needed to consult a historian in order to make his point any more valid, but he could probably have done with a historian proofreader to tidy up any flowery language that might detract from the overall message.

Knowledge on how to make things is ephemeral, is constantly lost and has to be rediscovered even in the modern world. People whose day job is playing meaningless language games don't have any appreciation of how much idiosyncracy goes into doing even simple technical tasks.