I mean that the masks can and do stop some droplets and larger particles, but smaller particles pass through and around them readily. It seems like really small particles might be causing infections with newer variants. But I'm also not sure what we even know for sure about this at the moment. A lot of mask research has been don with modeling or lab setups to spray liquids through them. The narrower set of real world studies cast a lot of doubt on anything but N95s worn properly. So I'm not sure where that leaves us.