Even that is overselling it:

https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD...

> Key messages

> We are uncertain whether wearing masks or N95/P2 respirators helps to slow the spread of respiratory viruses based on the studies we assessed.

> Hand hygiene programmes may help to slow the spread of respiratory viruses.

> There is uncertainty about the effects of face masks. The low to moderate certainty of evidence means our confidence in the effect estimate is limited, and that the true effect may be different from the observed estimate of the effect.

> Hand hygiene is likely to modestly reduce the burden of respiratory illness, and although this effect was also present when ILI [influenza-like illnesses] and laboratory‐confirmed influenza were analysed separately, it was not found to be a significant difference for the latter two outcomes.

> Our confidence in these results is generally low to moderate for the subjective outcomes related to respiratory illness, but moderate for the more precisely defined laboratory‐confirmed respiratory virus infection, related to masks and N95/P2 respirators.

> Relatively low numbers of people followed the guidance about wearing masks or about hand hygiene, which may have affected the results of the studies.