The argument, which doesn't seem insane, is that this film is useful because it is particularly optically clear and strong, which are not properties I would have expected from cellulose. I agree 17 days is too short, but that seems like an interesting opportunity for future research. I would highlight that the number is 17 days when buried in wet soil, not sitting around on a shelf. Cardboard will break down when buried in wet soil, yet we use it extensively in packaging without issue.