As a general rule, I don't take this kind of analysis via repeated repeated repeated repeated repeated repeated repeated application of Bayes' Rule with somewhat-to-completely arbitrary probabilities at each step very seriously. At all.
It's a kind of gish gallop [1] with additional window dressing purporting to wrap it all up into one easy number. From a probabilistic point of view it ignores any dependency between observed facts, which is a serious issue but not necessarily the most damning one.
This particular case is even worse than usual. According to a quick Ctrl-F-aided skim of the document, the author doesn't identify a single fact that increases the probability of zoonotic origin, which is extremely suspicious. If every single available fact in a complicated issue points to the same conclusion that's probably because you are messing with your facts, not because that's how things actually are.
After noticing the one-sided-ness of the Bayesian updates I rolled my eyes and closed the tab.