Yes, science changes, this is from March, blah, blah, blah. My point in posting is that this is the "most respected expert" speaking very confidently and definitely and essentially dismissing the effectiveness.
This one study doesn't prove or disprove anything other than what sized droplets are filtered by various materials. Evidence of case numbers from places with mask mandates would argue that they aren't very effective. Through Florida's summer spike, the worst performing counties had mask mandates.
The only way to really have scientific proof would be two similar places with similar population density and demographics and starting point for cases per day where they all have the exact same measures in place except everybody in one place wears cloth face coverings and nobody does in the other and see what the data shows.
I ask again, if they work so well (and this study says they work REALLY well), then why can't I be in a full stadium or arena as long as everybody wears one? Or, why do I have to quarantine for 14 days if I enter PA if I have to wear a mask (even outdoors) the whole time I'm there anyway?