Technological transfer can be hard to prove unless there is some high-status person doing it and having it documented as part of the process.

Read a paper in history of technology that argued that pre-Gutenberg printing was established in Arab lands independent of Chinese printing. This was shown in part by way of the low status of Arab printing, imported habits from China in general having high status. But because of the low status, it is rarely mentioned - I think there was a quote on whores, thieves and book-printers in the paper - meaning the amount of evidence is small. The author in the end argue that it is possible that printing moved with printers into Italy, where they for lack of local language focused on printing pictures, like Tarot cards. And that way it can have spread to Germany.

Arab printing was apparently out-competed by the more high-status habit of writing.

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