I certainly hope the similarities with Marek's disease reaching 100% mortality begin and end there. What I can personally extrapolate is that allowing or even advising vaccinated people not to wear masks and distancing is rather dangerous.
For the pre-2020 studies, they were more or less in agreement that masks didn't help, even in healthcare workers, who tend to be better trained and more compliant with masking protocols. Indeed Macintyre et al provides strong evidence of the risks of cloth mask wearing; while this study compared cloth masking to standard practice, not no-masking, it at a minimum establishes the very real risks of cloth mask wearing: https://pubmed.ncbi.nlm.nih.gov/25903751/
It's a virus where transmission is heavily influenced by water droplets. Masks limit the reach of water droplets from the nose and mouth.
Also it is unlikely for there to be a large study for ethical reasons (if wearing a mask might help, you can't get a control group).
> it at a minimum establishes the very real risks of cloth mask wearing
That is a pretty gross misreading of a study which has no non-mask control group and looked very different conditions to the pandemic