Context: A few issues.

1. When a study results in statistically insignificant difference, it often means it was not large enough to determine whether there's a difference.

In fact, fewer mask wearers tested positive for antibodies, but the incidence rate was too low, given the sample size, to rule out random chance. If there had been ten times more participants and the same proportions, they would have been significant.

The results could also not prove Hitchen's proposition—that there is no difference—it's jus a null result. The incidence is simply too low to determine one way or another.

2. Saying that it's “conclusive masks don’t work” misses the mark in a second way. Masks are primarily thought to work as source control—preventing people from spreading droplets as they speak. This study didn't test that. It tested respiratory protection. https://blogs.cdc.gov/niosh-science-blog/2020/09/08/source-control/

As the paper says: “The findings…should not be used to conclude that a recommendation for everyone to wear masks in the community would not be effective in reducing SARS-CoV-2 infections, because the trial did not test the role of masks in source control” https://www.acpjournals.org/doi/10.7326/M20-6817