It's more of a confirmation thing, I think. We've been pretty sure about Covid being airborne since early 2020. This probably helps convince some of the few that insist it isn't.
They don’t help at all with aerosol transmission.
So basically the entire world is crazy to mandate it unless it’s minimum kn95 or n95 masks.
Many many people don’t want to accept its aerosol transmission because it means it’s much harder to do anything about it.
"Here, we measured outward emissions of micron-scale aerosol particles by healthy humans performing various expiratory activities while wearing different types of medical-grade or homemade masks. Both surgical masks and unvented KN95 respirators, even without fit-testing, reduce the outward particle emission rates by 90% and 74% on average during speaking and coughing, respectively, compared to wearing no mask, corroborating their effectiveness at reducing outward emission."
Double cloth had a higher but not statistically significant increase in particle count (so equivalent to being unmasked) while vented N95s reduced particle surprisingly well.
What I did strange is that the cloth masks are mostly stuffier and harder to breathe than the surgical ones, which filter much better.
The FFP ones are of course the worst to use but also the best at filtering.
Either way I can't wait till we can safely get rid of all of them though... I wish there were powered ones with fans to pull in filtered but fresh air. But the only one I've seen is the Razer Hydra and it's always out of stock. It's also huge and looks like a WW2 gas mask so it's not really street smart.
That's outward transmission when the wearer is already infected, which has nothing to do with mask protection of the uninfected.