Hi. Actually guy with a genetics degree here and hefty immunology course load. Wife is a public health RN. And I read journal articles and studies because I'm a nerd like that/
Masks for general public use are NOT effective in preventing transmission. The vast majority of people wear masks incorrectly (removing them to talk, not practicing proper hygiene, not maintaining a sterile zone) and they have been proven to increase risk of transmission via a false sense of security. SARS-CoV-2 is droplet transmission and only aerosolized by certain medical procedures, so while an infected person wearing as mask is likely to reduce transmission via surfaces, MORE effective is STAYING THE **** HOME and having non-symptomatic people WASH THEIR HANDS and MAINTAIN A DISTANCE OF 2 METERS. In other words, the three bits of advice that every public health authority the world over is giving out. Recommending masks does nothing to prevent transmission, and creates a run on medical PPE - which we already saw and there are still shortages - by people who don't actually need it. Medical professionals need medical grade masks (surgical, N95, N100, P100) - if everyone else wants to wear a cloth or non-medical masks that's their option (which the WHO said from the beginning) but they do very, very little to stop or slow transmission.
The difference in Asian countries is not masks. It's aggressive distancing, rapid and aggressive test-and-trace, and collectivist cultures that prioritize following the instructions of authorities to everyone's benefit unlike the "MUH FREEDUMS!" asshats in most Western democracies.
So no, the WHO's advice on masks was not incorrect. It was evidence-based best-advice designed to prevent false sense of security leading people to violate the other public health orders, and to keep precious PPE supplies from being bought and hoarded by private individuals.And if you don't believe me.
That's influenza modelling/review data, which actually does readily aerosolize.
TL;DR: Outside of a medical / close-contact setting, masks are nothing more than a feel-good placebo. Maintaining a proper social distance will do more to prevent transmission than wearing a mask, particularly because mask wearers are more likely to engage in risk behaviour like touching the mask, touching their face, contaminating the protective field with mask removal with gloves or unwashed hands, and not following distancing protocols out of a false sense of security.